Book of Abstracts Book of Abstracts - Universität Konstanz

Symposium on
Size Selected Clusters
Book of
Abstracts
28 February - 3 March 2005 in Brand / Austria
http://www.s3c.uni-konstanz.de/

The S 3 C –
Symposium on Size Selected
Clusters
was generously supported by:
• German Science Foundation
• Varian

Table of Contents
FULL LENGTH TALKS AND HOT TOPICS......................................................................... 1
POSTERS.................................................................................................................................. 33
CARBON 35
CHEMISTRY 43
DYNAMICS 63
MAGNETISM 77
MATERIALS 83
METHODS 91
METALS 101
MOLECULAR CLUSTERS 113
PHASE TRANSITIONS 121
RARE GASES 127
SEMICONDUCTORS 135
SOLVATIONS 141
SURFACE 147
AUTHOR INDEX.................................................................................................................... 167
� Poster Session A (Monday evening): Metals, Molecular Clusters, Phase
Transitions, Rare Gases, Semiconductors, Solvations, Surface
� Poster Session B (Wednesday evening): Carbon, Chemistry, Dynamics,
Magnetism, Materials, Methods
� The poster numbers are given at the top of the abstracts which can be found in
the author index at the end of this book.

Full Length Talks
and Hot Topics
1

Metallic clusters and oxygen
Catherine Bréchignac
Laboratoire Aimé Cotton, CNRS, Bâtiment 505, Université Paris Sud, 91405 Orsay cedex, France
The interaction between metallic substance and oxygen is one of the most important
chemical and biological process in nature. This talk will discuss two aspects of oxygen
interaction with matter at nanometer-scale.
The first part of the talk deals with the interaction between metallic clusters and oxygen. Here
cluster acts as finite reservoir of electrons and it is shown how the reactivity strongly depends
on cluster size.
In a second part the cluster acts as a vehicle to bring oxide molecule locally on supported
islands. Using fractal islands as a test case for non-equilibrium morphologies, we show evidence
of oxide driven elongated pearled shapes similar to those observed in pearling instability of
membrane tubes with anchored polymers. Such a similarity indicates that the relaxation of
fractals shares the same universality as the shape transition in neurons and membrane tubes.
3

4
The Disapperarance of Nobility: Reactivity Studies on free Gold and
Silver Clusters
Ludger Wöste
Freie Universität Berlin, Institut für Experimentalphysik, Arnimallee 14, D-14195 Berlin, Germany
Contrary to the bulk metal the clusters of noble metals are very reactive. The process of
gold sensitisation in silver photography is a prominent example. Most exciting in this regard is
the non-scalable size regime below about 100 atoms per particle [1], where the physical
properties of noble metal clusters show very pronounced size and charge effects. Their
comprehension requires a clear identification of their geometries and electronic structures. We
investigated chemical reactions of mass-selected gold and silver clusters in a temperature
controlled rf-ion trap setup. Product ion concentrations as a function of storage time enable the
determination of reaction kinetics and reaction mechanisms on free clusters. As an example, the
CO combustion reaction on small gold clusters is studied. It is known that supported gold
clusters with few atoms up to nm size exhibit relevant catalytic properties. Our ion trap
measurements reveal catalytic activity already for negatively charged gold dimers. When the
reaction kinetics are investigated as a function of temperature, intermediate products with CO
and O2 co-adsorbed can be isolated [2]. In contrast, small atomic silver clusters have not been
found relevant for catalytic oxidation processes so far. Our investigations show for the first time
evidence for a strongly size dependent catalytic activity of Agn- (n=1-13) [3]. In order to
elucidate the details of their reaction dynamics, femtosecond pump-probe experiments were
performed on the educts, products and intermediates.
References
[1] U. Landman, Int. J. Mod. Phys. B 6, 3623 (1992).
[2] L. D. Socaciu, J. Hagen, T. M. Bernhardt, L. Wöste, U. Heiz, H. Häkkinen, U. Landman:
“Catalytic CO oxidation by free Au2-: Experiment and theory”, J. Am. Chem. Soc. 125, 10437
(2003).
[3] L. D. Socaciu, J. Hagen, J. Le Roux, D. Popolan, T. M. Bernhardt, L. Wöste,
S. Vajda: “Strongly cluster size dependent reaction behavior of CO with O2 on free silver cluster
anions”, J. Chem. Phys. 120, 2078 (2004).

Infrared Spectroscopy of Metal Ion Complexes: Models for Metal
Ligand Interactions and Solvation
Michael A. Duncan
Department of Chemistry, University of Georgia, Athens, GA 30602
maduncan@uga.edu
http://www.arches.uga.edu/~maduncan
Weakly bound complexes of the form M + -Lx (M=Fe, Ni, Co, etc.; L=CO2, C2H2, H2O,
benzene, N2) are prepared in supersonic molecular beams by laser vaporization in a pulsednozzle
cluster source. These species are mass analyzed and size-selected in a reflectron time-offlight
mass spectrometer. Clusters are photodissociated at infrared wavelengths with a Nd:YAG
pumped infrared optical parametric oscillator/amplifier (OPO/OPA) laser or with a tunable
infrared free-electron laser. M + -(CO2)x complexes absorb near the free CO2 asymmetric stretch
near 2349 cm -1 but with an interesting size dependent variation in the resonances. Small clusters
have blue-shifted resonances, while larger complexes have additional bands due to surface CO2
molecules not attached to the metal. M + (C2H2)n complexes absorb near the C-H stretches in
acetylene, but resonances in metal complexes are red-shifted with repect to the isolated
molecule. Ni + and Co + complexes with acetylene undergo intracluster cyclization reactions to
form cyclobutadiene. Transition metal water complexes are studied in the O-H stretch region,
and partial rotational structure can be measured. M + (benzene) and M + (benzene)2 ions (M=V, Ti,
Al) represent half-sandwich and sandwich species, whose spectra are measured near the free
benzene modes. These new IR spectra and their assignments will be discussed as well as other
new IR spectra for similar complexes.
5

6
Diffuse Electron States
Kit H. Bowen, Jr.
Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, USA
The extra electron in valence (conventional) anions resides in an orbital which is firmly
grounded on the nuclear framework of the system, i.e., the extra electron is localized. Likewise,
when such anions are solvated and become anion-molecule complexes, the extra electron
usually remains localized with the anion. During photodetachment of the excess electron from
such a cluster anion, this sub-anion acts as the chromophore, and the photoelectron spectrum
reflects the characteristics of that anion, albeit stabilized and spectrally shifted to higher electron
binding energy.
In other cluster anions, however, the excess electrons are more delocalized, even though
they remain closely associated with their nuclear frameworks. There is, however, still another
class of molecular and cluster anions in which the excess electrons are neither localized nor
closely associated with their nuclear frameworks, and these are anions with highly diffuse,
excess electron distributions. Examples include dipole bound anions, quadrupole bound anions,
double Rydberg anions, and some sizes of water cluster anions. While these species share the
characteristic of having spatially diffuse excess electrons, they are otherwise bound by different,
albeit idealized interactions. The excess electron in dipole bound anions is chiefly bound by the
dipolar field of the corresponding neutral system, with the excess electron ballooning out into
space at the positive end of the molecular or cluster system. Similarly, the excess electron in
quadrupole bound anions is primarily bound by the quadrupolar field of the corresponding
neutral system. Double Rydberg anions are the negative ions of Rydberg radicals. Each one can
be thought of as a closed shell, cationic core which is enveloped by two Rydberg-like, highly
diffuse electrons. Also, many water cluster anion systems appear to exhibit diffuse excess
electron states of at least two types, with a third type being associated with internalizing
electron states.
In this talk, we will survey these different types of diffuse electron states, but we will focus
on double Rydberg anions, in part because they are the least well-known diffuse, excess electron
species. In particular, we will discuss the ammonia-based double Rydberg anions, (NnH3n+1) - ,
where n = 1- 7. Using anion photoelectron spectroscopy, we have measured electron affinities
of these species, found examples of solvated double Rydberg anions, and accessed the first
electronic states of several neutral Rydberg radicals by photodetaching electrons from their
corresponding double Rydberg anions. Insight into the nature of these species was further aided
by comparisons with the absorption measurements of Fuke on neutral Rydberg cluster-like
radicals and by several theoretical studies, especially those of Ortiz.

Model Gold Catalysts by Size-Selected Cluster Deposition
Sungsik Lee, Chaoyang Fan, Tianpin Wu, and Scott L. Anderson
Dept. of Chemistry, University of Utah, 315 S. 1400 E. Rm 2020, Salt Lake City UT 84112, USA
Planar model gold catalysts were prepared by deposition of size- and energy-selected gold
cluster cations, on well characterized supports in UHV. The CO oxidation reaction was used to
characterize the chemical behavior of the resulting samples. As shown in the figure, strongly
size-dependent activity is observed for room temperature CO oxidation on Aun/TiO2, with
significant activity observed for n ≥ 3. No activity is observed for Au/Al2O3. Detailed studies
over a wide temperature range, using x-ray photoelectron spectroscopy (XPS), ion scattering
spectroscopy (ISS), and CO thermal adsorption and desorption were used to probe the nature of
the samples resulting from cluster deposition. It is found that on titania, the gold migrates to
surface oxygen vacancy sites between 200 and 300K, and appears to be stably trapped at the
vacancies at room temperature. XPS shows that binding at the vacancies injects electron density
into the clusters, and absence of this effect on alumina is probably responsible for the observed
lack of activity. At T ≥ 450 K, significant agglomeration occurs. Correlations of activity with
the cluster morphology and ability to bind CO and O2, both on the clusters, and in adjacent
substrate sites, will be discussed.
C 16 O 18 O+ intensity (arb.)
7e+5
6e+5
5e+5
4e+5
3e+5
2e+5
1e+5
0
CO oxidation
TiO2 Au1 Au2 Au3 Au4 Au5 Au6 Au7
7

8
Structural Order in Metal Clusters: Dependence on Size and Charge
State
Joel H Parks
Rowland Institute at Harvard, Cambridge, Massachusetts 02142
Trapped ion electron diffraction (TIED) has been applied to Ag and Au cluster ions
produced by a sputter discharge aggregation source. A specific cluster size is selectively stored
in an rf ion trap in which the trapped ions are annealed and brought into thermal equilibrium
with a background He gas. The stored ions are then exposed to a high energy electron beam and
electron scattering is imaged by a multichannel plate detector onto a phosphor screen.
Diffraction patterns are collected by a CCD camera and analyzed to extract the molecular
interference directly related to the arrangement of atoms in the mass selected cluster.
Following a brief introduction to TIED experiment and analysis, this talk will present recent
measurements for Agn + cations, and Aun -/+ cation and anion clusters. Two principal results will
be discussed: the transition from local to global five-point order in Agn + clusters over the size
range 36≤n≤55, and the dependence of Aun -/+ structures on charge state for n=20,32,38 and 55.
Diffraction data will be compared with isomer structures predicted by density functional
calculations and molecular dynamic simulations. Experimental opportunities for diffraction
measurements will be briefly considered.

Ultra-stable Hetero-nuclear Microclusters of (CdSe)33 and (CdSe)34
Atsuo Kasuya 1 , Rajaratnam Sivamohan 1 , Yurii A. Barnakov 1 , Igor M. Dmitruk 1,6 , Takashi Nirasawa 2,3 ,
Grzegorz Milczarek 1 , Sergiy V. Mamykin 1 , Volodymyr R. Romanyuk 1 , Kazuyuki Tohji 2 , Valachandran
Jeyadevan 2 , Kozo Shinoda 2 , Toshiji Kudo 3 , Osamu Terasaki 4 , Zheng Liu 4 , Tetsu Ohsuna 5 , Rodion V.
Belosludov 5 , Vijay Kumar 1,5 , Vijayaraghavan Sundararajan 1 , Yoshiyuki Kawazoe 5
1 Center for Interdisciplinary Research, Tohoku University, Sendai, 980-8578, Japan
2 Department of Geoscience and Technology, Tohoku University, Sendai, 980-8579, Japan
3 Bruker Daltonics K.K., Kanagawa-ku, Yokohama, 221-0022, Japan
4 Department of Physics, Tohoku University, Sendai, 980-8578, Japan
5 Institute for Material Research, Tohoku University, Sendai, 980-8577, Japan
6 Kyiv National Taras Shevchenko University, Kyiv, 03022, Ukraine
Time-of-Flight mass spectra reveal that nanoparticles, (CdSe)n, grown in solution can be mass
selected at atomic level by reverse micelle method. This method allows us to produce
macroscopic quantity of (CdSe)33 and (CdSe)34 by making use of their highly selective
stabilities in reverse micelles [1]. This preferential growth at particular n’s depicted by mass
spectra suggests that the structure of these particles is quite different from a bulk fragment and
is high-symmetric (CdSe)28 cage incorporating 5 or 6 CdSe pairs inside and forming sp 3
network. Similar selective stabilities have been found in CdS and other A II B VI compounds,
demonstrating that such highly stabilied clusters may be found in a variety of compound
systems.
Figure 1. Time-of-flight mass spectra of positive ions from (CdSe) n prepared in toluene (curve 1), and from powders
of bulk CdSe (curve 2) and CdS (curve 3). Suggested structure of (CdSe) 34 cluster.
References
[1] Kasuya A., Sivamohan R., Barnakov Yu., Dmitruk I., et al, Nature Materials 3, 99 (2004).
9

Dynamics and spectroscopy of anion clusters and helium nanodroplets
10
Daniel M. Neumark
Department of Chemistry, University of California, Berkeley, CA. USA 94720, and Chemical Sciences
Division, Lawrence Berkeley National Laboratory, Berkeley, CA USA 94720
Recent results on the spectroscopy and dynamics of water cluster anions and helium
nanodroplets will be presented. Mass-selected (H2O)n - and (D2O)n - anions were studied using
one-photon and time-resolved photoelectron imaging. The one-photon studies established the
existence of both internal and surface states of water clusters anions, and showed that one can
switch between isomers by varying ion source conditions. The time-resolved studies yielded
excited state lifetimes for both isomers, showing dramatically different dependence on cluster
size. Extrapolation of the internal conversion rates for the internal states to the bulk limit
strongly supports the “non-adiabatic” relaxation mechanism proposed for the hydrated electron
in aqueous solution.
The photoionization and photoelectron spectroscopy of He nanodroplets was investigated using
synchrotron radiation at the Advanced Light Source at Lawrence Berkeley National Laboratory.
Photoelectron images were obtained at photon energies below and above the ionization potential
of atomic He (24.6 eV). The images below the IP were dominated by extremely slow electrons,
with an average energy of < 1 meV, believed to originate from excitation and autoionization of
a Hen subunit within the cluster followed by thermalization of the electron before it leaves the
cluster. The images above the IP are very different, showing photoelectron signal at higher
energy than that seen from atomic He. This high energy signal is attributed to direct detachment
to the attractive region of Hen+ potential energy surfaces.

Tailoring functionality of clusters by size, structures and lasers
Vlasta Bonačić-Koutecký
Humboldt Universität zu Berlin, Institut für Chemie, Brook-Taylor-Strasse 2,
D-12489 Berlin, Germany, e-mail: vbk@chemie.hu-berlin.de
Theoretical exploration of cluster properties for which each atom counts will be presented
for the following topics:
1. Chemical reactivity of nobel-metal oxides as foundation for design of nanoscale
catalytic materials.
2. Emissive properties of silver particles at silver oxide defects as attractive candidates for
optical data storage.
3. Ultrafast dynamics and its control by tailored laser fields in clusters and in their
complexes with biomolecules for selection of reaction channels and of photochemical
processes.
4. Importance of mutual interaction between theory and experiment for all three subjects
will be illustrated.
11

A new infrared spectroscopy technique for structural studies of massselected
neutral polar molecular species without chromophore
12
B. Lucas, F. Lecomte, G. Grégoire, Y. Bouteiller, J.-P. Schermann, C. Desfrançois
Lab. de Physique des Lasers, CNRS-Univ. Paris-Nord, 93430 Villetaneuse, France
We will present a new infrared spectroscopy technique for structural studies of massselected
neutral polar molecules or complexes without chromophore [1]. In these experiments,
we use dipole-bound anion formation, as a totally non-perturbative ionization method. Anion
signal depletion allows us to monitor IR absorption, in between 2700 and 3800 cm -1 , on massselected
neutral species. For weakly bound complexes, with typical H-bond dissociation
energies about 1500 cm -1 , IR absorption indeed leads to fast vibrational predissociation prior to
ionization. For both isolated molecules and complexes, the very weak excess electron binding
energy (typically 100 cm -1 ) in dipole-bound anions also allows for vibrational autodetachment
due to IR absorption. In both cases, the signature of IR absorption by the neutral species is a
loss in the dipole-bound anion signal at the corresponding mass. This is an alternative technique
to the IR-REMPI technique when the neutral species do not possess any chromophore.
We will discuss results on small molecules and clusters containing water and formamide:
water dimer, formamide-water complex, isolated formamide and formamide dimer. These four
test-cases exemplify the capabilities and limitations of this technique and allow us to plan for
future technical improvements in order to gain sensitivity for further experiments on molecules
and complexes of biological interest. Experimental IR spectra will be interpreted with the help
of quantum chemistry calculations. In particular, the use of anharmonic frequency calculations
will be discussed.
relative anion signal depletion
0.4
0.2
0.0
-0.2
-0.4
-0.6
-0.8
-1.0
free CH
2850 2900 2950
bonded
NH / OH
free NH
?
3400 3450 3500 3550
frequency (cm -1 )
free OH
3700 3750
IR spectrum of mass-selected neutral formamide-water complexes obtained from dipole-bound anion signal
depletion. Small squares correspond to relative depletion values averaged over 3 independent measurements while
full thick lines correspond to a smooth over 3 adjacent points. Experimental line positions are indicated by thin dash
lines and theoretical frequencies are located by full (anharmonic values) or dash (scaled harmonic values) bars. The
question mark corresponds to a line that is not assigned.
References
[1] B. Lucas, F. Lecomte, B. Reimann, H.-D. Barth, Gilles Grégoire, Y. Bouteiller, J.-P. Schermann,
C. Desfrançois, Phys. Chem. Chem. Phys. 6, 2600 (2004).

The hydrogen transfer reaction: from molecular clusters to proteins
C. Jouvet 1 , H. Kang 1 , C. Dedonder-Lardeux 1 , G. Grégoire 2 , C. Desfrançois 2 , J-P. Schermann 2 , M. Barat 3
and J. A. Fayeton 3
1 Laboratoire de Photophysique Moléculaire du CNRS et Laboratoire ELYSE, Bat349, Université Paris-
Sud, 91405 Orsay, France.
2 Laboratoire de Physique des Lasers du CNRS, Institut Galilée, Université Paris-Nord, 93430
Villetaneuse, France.
3 Laboratoire des Collisions Atomiques et Moléculaires du CNRS, Université Paris-Sud, 91405 Orsay,
France.
Four years ago we have demonstrated that the excited state reaction of phenol-amonnia
clusters is an H atom transfer leading to the formation of hypervalent NH4(NH3)n clusters 1, 2 , and
not by a proton transfer as suggested by the liquid phase experiments. This first observation lead
to the developement of a more general model 3 where a surprisingly simple and general
mechanistic picture for the nonradiative decay of aromatic biomolecules such as nucleic bases
and aromatic amino acids has been suggested.
The key role in this model is played by an excited singlet state of πσ* character, which has
a repulsive potential-energy function with respect to the stretching of OH or NH bonds. The
1 πσ∗ potential-energy function intersects not only the bound potential-energy functions of the
1 ππ∗ excited states, but also that of the electronic ground state 3 . Via predissociation of the 1 ππ∗
states and a conical intersection with the ground state, the � πσ* state triggers an internalconversion
(IC) process. The lifetime of the optically excited � ππ∗ state is governed by the first
intersection which determines the barrier for IC process, and varies from one molecule to the
other depending largely on the energy gap between the 1 πσ∗ and the 1 ππ* states.
In clusters of phenol or indole 4 and ammonia, calculations predict that the H transfer leads
to the formation of hydrogenated ammonia clusters NH4(NH3)n through an avoided crossing
between the 1 ππ∗ and the 1 πσ∗ states 5 . In this system the reaction seems to proceed via
tunneling, since the process is fast in the hydrogenated species and considerably slower for
deuterated species 6-7 . We recently demonstrated that this model also applies in protonated
aromatic amino acid (tryptophan, tyrosine) and explains why the excited state lifetime of
protonated Tryptophan (400fs) 8 is ten times shorter than the lifetime of protonated Tyrosine.
References
[1] G. Pino, G. Gregoire, C. Dedonder-Lardeux, C. Jouvet, S. Martrenchard and D. Solgadi, Physical
Chemistry Chemical Physics, 2000, 2, 893-900.
[2] G. A. Pino, C. Dedonder-Lardeux, G. Gregoire, C. Jouvet, S. Martrenchard and D. Solgadi, J.
Chem. Phys., 1999, 111, 10747.
[3] A. L. Sobolewski, W. Domcke, C. Dedonder-Lardeux and C. Jouvet, Phys. Chem. Chem. Phys.,
2002, 4, 1093-1100.
[4] C. Dedonder-Lardeux, D. Grosswasser, C. Jouvet and S. Martrenchard, Physchemcomm, 2001,
1-3.
[5] A. L. Sobolewski and W. Domcke, J. Phys. Chem. A, 2001, 105, 9275.
[6] G. Gregoire, C. Dedonder-Lardeux, C. Jouvet, S. Martrenchard, A. Peremans and D. Solgadi,
Journal of Physical Chemistry A, 2000, 104, 9087-9090.
[7] S. Ishiuchi, K. Daigoku, M. Saeki, K. Hashimoto, M. Sakai and M. Fujii, J. Chem. Phys., 2002,
117, 7077.
[8] H. Kang, C. Jouvet, C. Dedonder-Lardeux, S. Martrenchard, G. Grégoire, C. Desfrançois, J.-P.
Schermann, M. Barat and J. A. Fayeton, P.C.C.P., 2004, to be published.
13

14
Immobilisation of proteins by size-selected nanoclusters on surfaces
Richard E. Palmer
Nanoscale Physics Research Laboratory, School of Physics and Astronomy, The University of
Birmingham, Birmingham B15 2TT, UK
r.e.palmer@bham.ac.u
www.nprl.bham.ac.uk
The controlled deposition of size-selected nanoclusters represents a novel route to the
fabrication of nanostructured surfaces, generating lateral features of size 1-10 nm. This is
precisely the size scale of biological molecules and provides a new method to immobilize
individual proteins, with potential applications in structural biology, protein complex formation
and high throughput medical diagnostics (microarrays).
Scaling relations which describe both the implantation [1] and pinning [2] of the clusters
enable the controlled preparation of 3D, nanoscale surface features, stable to temperatures as
high as 400°C. In particular, we report the pinning of size-selected AuN clusters (N = 1 – 100) to
the hydrophobic graphite surface to create films of arbitrary, sub-monolayer density. Gold
presents an attractive binding site for sulphur and thus potentially for the cysteine amino acid
residues in proteins (which contain a thiol, SH, group), suggesting the possibility of residuespecific
immobilization of oriented protein molecules.
AFM measurements in liquid (buffer) solution show that GroEL chaperonin molecules
(ring-shaped molecules with diameter 15 nm), which contain free cysteine residues, bind to the
clusters and are immobilised [3]. Both peroxidase molecules [4], in which the cysteine residues
pair up to form disulphide bonds, and oncostatin molecules can similarly be immobilised. In
both cases protein clusters are also formed. By contrast, green fluorescent protein (GFP) and
luciferase molecules do not bind to the nanoclusters. The behaviour of the different protein
molecules is predicted by a model, based on molecular surface area calculations, which
considers the “accessibility” of cysteine (and other) residues at the outer surface of the folded
protein. The results demonstrate the ground rules for, and generality of, protein immobilisation
by metal cluster films.
Finally, I will discuss ongoing experiments with human IgG molecules which seem to
present the first evidence that protein immobilization depends on cluster size.
References
[1] S. Pratontep, P. Preece, C. Xirouchaki, R.E. Palmer, C.F. Sanz-Navarro, S.D. Kenny and R. Smith,
Phys. Rev. Lett. 90 055503 (2003).
[2] S.J. Carroll, S. Pratontep, M. Streun, R.E. Palmer, S. Hobday and R. Smith, J. Chem. Phys. 113
7723 (2000); also Nature (News & Views) 408 531 (2000).
[3] R.E. Palmer, S. Pratontep and H.-G. Boyen, Nature Materials 2 443 (2003).
[4] C. Leung, C. Xirouchaki, N. Berovic and R.E. Palmer, Adv. Mater. 16 223 (2004).

Atomic and Molecular Architecture at Surfaces
Klaus Kern
Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart
klaus.kern@fkf.mpg.de
A promising route toward the realization of functional nanosystems is the exploitation of
nature’s inherent drive to generate complexity. The transcription of the corresponding
organization principles to artificial compounds and environments comprises intriguing
perspectives. We emphasize the conductance of self-organized growth processes at well-defined
surfaces. The atomistic insight gained into the underlying mechanisms and interactions is used
to control the formation of low-dimensional atomic and molecular architectures. This knowhow
opens up new avenues in engineering nanomaterials of well-defined shape, composition
and functionality to be harnessed for future technological applications.
15

Size-Selected Aun and Agn Clusters on Rutile TiO2 (110) (1x1) Surfaces
Probed by UHV-STM
16
Steven K. Buratto, Xiao Tong, Lauren Benz, Andrei Kolmakov, Paul Kemper, Steeve Chrétien, Horia
Metiu, and Michael T. Bowers
Department of Chemistry and Biochemistry, University of California, Santa Barbara
Santa Barbara, CA 93106-9510, United States of America
Catalysis of the oxidation of CO and small olefins by nanoclusters of Au and Ag on oxide
supports is known to be strongly dependent on the size of the cluster and its interaction with the
oxide support. In our group we have probed the size dependence by depositing size-selected
clusters of Agn + and Aun + (n = 1-7) from the gas phase onto single crystal rutile TiO2 (110) (1x1)
surfaces at room temperature under soft-landing (< 2 eV/atom) conditions. We analyze the
clusters on the surface using ultra-high vacuum scanning tunneling microscopy (UHV-STM)
and compare the resulting structures with theory. In the case of Ag + and Ag2 + clusters deposited
under soft-landing conditions (Figure 1), we observe large, sintered clusters indicating high
mobility for these species on the surface. For Agn + (n ≥ 3) clusters (also shown in Fig. 1)
deposited under soft-landing conditions, however, we observe a high density of intact clusters
bound to the surface and no large, sintered clusters indicating that these species have very
limited mobility on the surface.
Figure 1. STM Images of the titania surface after the deposition of Ag 1, Ag 2, and Ag 3, respectively, from left to right.
All images are 100 nm x 100 nm, insets are ~ 7 nm x 7 nm.
In the case of Aun + clusters, we observe large, sintered clusters only from the deposition of Au +
and a high density of intact clusters from the deposition of Aun + (n ≥ 2) as depicted in Figure 2.
In cases where we observe intact clusters we can observe the binding site and geometry in the
STM image and compare these with structures calculated using density functional theory (DFT)
as well as structures observed in the gas phase.
Figure 2. STM Images of the titania surface after the deposition of Au 1, Au 2, Au 3, Au 4 and Au 7, respectively, from
left to right. All images are 100 nm x 100 nm, insets are ~ 7 nm x 7 nm.

Magnetic Properties of Deposited Transition Metal Atoms and
Clusters
Matthias Reif, Leif Glaser, Michael Martins, Wilfried Wurth
Insitut für Experimentalphysik, Universität Hamburg, Luruper Chaussee 149,
Hamburg, D-22761, Germany
From a fundamental point of view size-selected transition metal clusters allow to study the
transition from the magnetic properties of atoms to those of the respective solids as a function of
cluster size. For possible future applications these clusters have to be supported on a substrate of
embedded in a matrix where cluster-support interaction will influence theier physical properties
as well. We have therefore started to investigate the magnetic properties of small transition
metal clusters in contact with ferromagnetic substrates as a function of the number n of cluster
atoms in the size region from n=2 to n=20.
To achive thos goal we have developed a UHV-compatible cluster source, which enables us to
investigate size selected transition metal clusters deposited in-situ under UHV conditions on
solid surfaces using soft X-ray spectroscopy at third generation synchrotron radiation sources.
This contribution will discuss especailly x-ray magnetic circular dichroism (XMCD) studies of
size selected deposited clusters and recent experimental results of supported 3d and 4d transition
metal clusters will be presented. For iron clusters [1,2] on nickel a strong size dependence of the
spin- and orbital moment, which could be measured independently with the XMCD method, are
found. In particular the orbital moment per iron atom is strongly enhanced as compared to the
values of bulk solid or ultrathin films.
Recent experimental and theoretical studies on chromium clusters in the size range from n=1 to
n=13 deposited on ultrathin ferromagnetic nickel and iron surfaces demonstrate the importance
of the substrate. Whereas for Cr clusters on Ni films no XMCD signal is found, for Cr clusters
on Fe films a strong decrease of the magnetic moment by a factor of 4 is found with increasing
cluster size. This effect can be interpreted in terms of a non-collinear coupling of the magnetic
moments within the cluster and relative to the surface [3]. Finally, first results on the magnetic
properties of deposited 4d transition metal atoms and dimers (Ru, Mo) will be given .
References
[1] J.T. Lau , A. Föhlisch, R. Nietubyc, M. Reif, and W. Wurth, Phys. Rev. Lettl. 89, 057202 (2002).
[2] J.T. Lau , A. Föhlisch, M. Martins, R. Nietubyc, M. Reif, and W. Wurth, New J. Of Phys. 4, 98.1
(2002)
[3] M. Reif, L. Glaser, M. Martins, W. Wurth, S. Lounis, and S. Blügel, in preparation.
17

Emergent physics and chemistry of clusters: Fermion/boson clusters in
quantum dots/traps, and nanocatalysis
18
U. Landman
University School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430, USA
We discuss several physical and chemical cluster phenomena that are emergent in nature.
Focus is placed on emergent symmetry-breaking physical processes resulting in formation of
electron crystalline clusters in 2D quantum dots, and on the breaking of trapped Bose-Einstein
condensates into Bose quantum crystallites, occurring as the inter-atomic repulsion is increased.
Emergent chemical cluster phenomena are discussed in the context of nanocatalysis by gold
nanoclusters, with an emphasis on clusters supported on metal-oxide surfaces (specifically
MgO), and the role of surface defects and cluster charging effects.

Cluster ferroelectricity
Walt de Heer
Georgia Institute of Technology
Experiments on beams of isolated Nb, Ta, V, Al clusters with up to 200 atoms, show that
these particles attain relatively large electric dipole moments at cryogenic temperatures. This
ferroelectric property cannot be reconciled with normal metallic behavior since the ferroelectric
state implies large internal electric fields. However various aspects of this state of matter appear
to be closely related to bulk superconductivity. For example, the effect only occurs in metals
that are superconductors in the bulk and a strong dependence even-odd alternation is observed.
The ferroelectric transition temperature is similar to the bulk Tc. A survey of the electronic
properties of these and other metallic clusters reinforce the superconducting pairing hypotheses
in these clusters.
19

20
Molecular Magnets in the Gas Phase: Stern-Gerlach Beam Deflection
Studies of Metal Clusters
Mark B. Knickelbein
Chemistry Division, CHM 200, Argonne National Laboratory, Argonne, Illinois 60439, USA
The study of transition metal clusters in the gas phase offers the opportunity to study the
emergence of novel magnetic behavior atom-by-atom, in the size range that bridges atomic and
bulk behavior. In this contribution, the results of Stern-Gerlach molecular beam deflection
studies of transition metal clusters will be presented. Bare manganese clusters (Mn5-99) exhibit
spatial deflections or broadening of magnitudes far in excess of those expected based on the
susceptibility of bulk manganese, indicating that clusters in this size range are magnetically
ordered. The magnitude of the magnetic moments (Figure 1), interpreted in light of recent
density functional theory calculations, suggest that Mn clusters in this size range are molecular
ferrimagnets. Recent magnetic deflection results for clusters composed of the Group IIIB
metals, Scn, Yn, and Lan, indicate that they are also molecular magnets. Several Group IIIB
clusters stand out as bona fide high-moment molecular magnets: Sc13 (6.0±0.2µb), Y8
(5.2±0.1 µb), Y13 (9.6±0.1 µb), and La6 (4.8±0.2 µb).
References
moment per atom (µ b )
2.0
1.5
1.0
0.5
0.0
12
13
10 20 30 40 50 60 70 80 90 100
Figure 1. Magnetic moments per atom for manganese clusters produced at 68K.
[1] M. Knickelbein, Phys. Rev. Lett. 86, 5255 (2001).
[2] M. Knickelbein, Phys. Rev. B 70, 014424 (2004).
19
n
57
Mn n

Oxidation Effects of the Small Chromium and Manganese Cluster
Ions
K. Tono, 1,2 A. Terasaki, 2 T. Ohta, 1 and T. Kondow 2
1 Department of Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
2 Cluster Research Laboratory, Toyota Technological Institute in East Tokyo Laboratory, Genesis
Research Institute, Inc., 717-86 Futamata, Ichikawa, Chiba 272-0001, Japan
Properties of transition-metal clusters are affected by reaction with foreign elements such as
nitrogen and oxygen. For example, it has been predicted that the magnetic property of a
chromium dimer is drastically changed by either nitridation or oxidation [1,2]. Motivated by
these theoretical studies, we investigated the electronic structures of the chromium- and
manganese-oxide cluster anions through measurements of photoelectron spectra and analyses
with the aid of the density functional theory (DFT). It was found that the spin magnetic moment
of Cr2O – is as large as 9 µB, while that of Cr2 – is 1 µB. This result shows that the spin coupling
between the chromium sites becomes ferromagnetic upon oxidation of Cr2 – whose chromium
sites are coupled antiferromagnetically [3,4]. The mechanism of the ferromagnetic spin coupling
is explained on the basis of the geometric and electronic structures obtained by the DFT
calculations. The oxygen atom at the bridge site weakens the strong bond between the
chromium atoms, which is responsible for the antiferromagnetic coupling in Cr2 – . In addition,
significant hybridization between chromium 3d and oxygen 2p orbitals allows electrons in the
same spin state to be transferred from the two chromium atoms to the oxygen atom.
Consequently the local spins on the chromium sites are bound to form a ferromagnetic coupling
in a similar scheme of the superexchange interaction encountered in solids. An oxidation effect
of a similar kind was found for Mn2O – , in which a ferromagnetic coupling between the local
spins (about 5.5 µB) at the manganese sites stabilizes its electronic structure [5,6].
Manganese clusters differ distinctly from chromium clusters; the manganese atoms are very
weakly bound because of the closed shell of 4s electrons. This is also true to singly charged
manganese cluster cations, MnN + (N=3–7), where the binding energy is found to be less than 1
eV/atom as reported in Ref. [7] and as shown further by the present measurements. The
structural specificity results from a weak van-der-Waals like interaction between the constituent
atoms, and is likely to change greatly if one introduces an oxygen atom into MnN + , because the
oxygen could glue manganese atoms in its vicinity. Actually we elucidated how the introduced
oxygen changes the geometrical and electronic structures of MnN + in photodissociation
experiments of MnNO + (N=3–5). In practice, the mass spectra of photodissociation products
from MnNO + were measured as a function of the photon energy of an excitation laser. The
results show that the oxygen atom and two manganese atoms form a Mn2O + core ion and the
other manganese atoms are weakly bound to the core ion. Analyses of the photodissociation
action spectra of MnNO + are now in progress in order to obtain detailed information on the
electronic and geometric structures.
References
[1] S. E. Weber, B. V. Reddy, B. K. Rao, and P. Jena, Chem. Phys. Lett. 295, 175 (1998).
[2] B. V. Reddy and S. N. Khanna, Phys. Rev. Lett. 83, 3170 (1999).
[3] K. Tono, A. Terasaki, T. Ohta, and T. Kondow, Phys. Rev. Lett. 90, 133402 (2003).
[4] K. Tono, A. Terasaki, T. Ohta, and T. Kondow, J. Chem. Phys. 119, 11221 (2003).
[5] K. Tono, A. Terasaki, T. Ohta, and T. Kondow, Chem. Phys. Lett. 388, 374 (2004).
[6] S. N. Khanna, P. Jena, W.-J. Zheng, J. M. Nilles, and K. H. Bowen, Phys. Rev. B 69, 144418
(2004).
[7] A. Terasaki, S. Minemoto, and T. Kondow, J. Chem. Phys. 117, 7520 (2002).
21

22
Electronic structure and spin polarization of dilute magnetic
semiconducting nanocrystals: a first principles approach
Xiangyang Huang 1 , Adi Makmal 2 , James R. Chelikowsky 1 , and Leeor Kronik 2
1 Department of Chemical Engineering and Materials Science and the Institute for the Advanced Theory
of Information Materials, University of Minnesota, Minneapolis 55455, USA
2 Department of Materials and Interfaces, Weizmann Institute of Science, Rehovoth 76100, Israel.
Bulk dilute magnetic semiconductors have attracted considerable attention in recent years
because they exhibit semiconducting and magnetic properties at the same time, potentially
enabling novel electronic devices that manipulate the electron spin in addition to its charge,
commonly known as “spintronic” devices. 1 Novel spintronic effects are expected at
nanocrystalline dilute magnetic semiconductors because the carrier confinement greatly
enhances spin-spin interactions.
Here, we present what we believe to be the first ab initio study of the electronic structure of Mncontaining
Ge, GaAs, and ZnSe nanocrystals, using a real-space pseudopotential-density
functional theory approach. We find that in all cases significant spin-polarization is formed and
that the magnetic moment distribution around the Mn atom displays clear chemical trends,
becoming more localized with increasing bond ionicity, as shown in Fig. 1. A detailed analysis
of the electronic structure reveals different patterns of level filling and ferromagnetic or antiferromagnetic
couplings. Importantly, the electronic structure exhibits considerable quantum
size effects. The electronic and magnetic properties of the dilute magnetic nanocrystals are
compared and contrasted with the properties of the corresponding bulk systems. Potential device
implications are discussed.
References
Figure 1. Distribution of the net magnetic moment for (from left to right)
passivated MnGe81,MnGa40As41, and MnZn40Se41 nanocrystals.
[1] S. A. Wolf, D. D. Awschalom, R. A. Buhrman, J. M. Daughton, S. von Molnar, M. L. Roukes A.
Y. Chtchelkanova, and D. M. Treger, Science 294, 1488 (2001).

Electronic structure and bonding in gold coated silica cluster: a nano
bullet for tumor
Q. Sun, Q. Wang, and P. Jena
Physics Department, Virginia Commonwealth University, Richmond, VA 23284, USA.
Recently an exciting application of gold coated silica nano-shells has been found in treating
tumor and cancer. The nano-shell consists of silica (SiO2) core of order 100 nm coated with
about 20 nm of gold. It absorbs near infrared light (NIR) and converts that light to heat, causing
irreversible thermal cellular destruction. When the nano-shells were incorporated into human
breast cancer cells in a test tube, and then exposed to NIR, 100 percent of the cancer cells were
killed. Motivated by this experiment we have investigated the coating of a small silica cluster
(of the order of a few nano-meters) with Au to understand (1) if such a small cluster can absorb
infrared radiation and (2) if so, does the mechanism for such absorption have electronic origin?
(3) How do Au atoms bind with silica core? We show for the first time that gold atoms bind to
silicon atoms with dangling bonds and serve as seeds for the growth of Au islands (Fig. 1a). The
large electron affinity of gold causes significant change in the electronic structure of silica
resulting in a substantial reduction in the HOMO-LUMO gap (Fig. 1 b), thus allowing it to
absorb near infrared radiation (Fig. 1 c). Our study suggests that a small cluster can have similar
functionality in the treatment of cancer as the large size nano-shell, but for a different
mechanism. The advantage of such small nano-bullet for targeting tumor and cancer is that it
can easily penetrate the crowded environments such as the biological milieu of cells and live
tissues for effective drug delivery.
Au
Au
References
Geometry
O
Si
Au
Energy (eV)
(a) (b) (c)
Figure 1. (a) Geometry, (b) HOMO-LUMO gap, and (c) optical spectra of Au 3-(SiO 2) 3.
[1] L.R. Hirsch, et al. PNAS 100 , 13549 (2003).
[2] Q. Sun, Q. Wang, B.K. Rao, and P. Jena, Phys. Rev. Lett. 93, 186803 (2004).
1
0
-1
-2
-3
-4
-5
-6
-7
-8
-9
-10
-11
(SiO 2 ) 3
Au 3 -(SiO 2 ) 3
Energy spectra
Optical absorption (arb.units)
7
6
5
4
3
2
1
Optic spectra
0
0 100 200 300 400 500 600 700 800 900 1000
Wave length (nm)
23

24
Low-temperature Oxidation of N2 on Supported Tungsten
Nanoclusters
Junichi Murakami 1 , Wataru Yamaguchi 2
1 Nanotechnology Research Institute, National Institute of Advanced Industrial
Science and Technology, Central 4, 1-1-1 Higashi, Tsukuba, 305-8562, Japan
2 Materials Research Institute for Sustainable Development, National Institute of
Advanced Industrial Science and Technology, 2266-98 Anagahora, Shidami,
Moriyama-ku, Nagoya, 463-8560, Japan
It is known that enzymes in organisms often contain nanoclusters composed of several
transition-metal atoms and sulfur or oxygen atoms. One of the famous examples of such
enzymes is the nitrogenase that carry out nitrogen fixation (conversion of N2 in air into
ammonia) at room temperature and 0.8 atm. Nitrogenase is known to carry several kinds of
nanoclusters, among which FeMo cluster (MoFe7S9) is believed to be most important for
activation and reduction of N2 at room temperature. The fact that the nanocluster-containing
enzymes carry out otherwise difficult chemical reactions suggests the nanoclusters are exotic
materials that can catalyze the reactions under mild conditions.
We recently started studying reactions of N2 on deposited transition-metal nanoclusters to
investigate whether they also have such catalytic activities. Size-selected tungsten nanoclusters
(Wn;n=2-6) are softlanded at room temperature on graphite (HOPG) surfaces that were
bombarded by Ar+ ions before the cluster deposition. Defects created by the ion bombardment
work as pinning centers for the clusters. The deposited nanoclusters are exposed to various
gases and chemical reactions of N2 on the clusters were investigated.
When the clusters at 140K were exposed simultaneously to N2 and H2O, it was found that N2O
forms on the clusters. This was observed by X-ray photoelectron spectroscopy(XPS) and
confirmed by thermal desorption spectroscopy(TDS). TDS measurements using isotopemers of
N2 and H2O revealed that N2, activated on the clusters, reacted with an O atom from H2O to
form N2O at a temperature as low as 140K. The details including cluster-size dependence of the
reaction will be presented at the symposium.
References
[1] W.Yamaguchi and J.Murakami, Chem. Phys. Lett. 378, 521 (2003).

Catalytic CO oxidation on ionic platinum clusters
O. Petru Balaj, Iulia Balteanu, Tobias Roßteuscher, Vladimir E. Bondybey, Martin K. Beyer
Department Chemie, Physikalische Chemie 2, Technische Universität München, Lichtenbergstraße 4,
85747 Garching, Germany
Cationic and anionic platinum clusters with up to 25 atoms are produced from isotopically
highly enriched platinum-195 ( 195 Pt, 97.28%) in a laser vaporization source, and their reactions
are investigated by Fourier transform ion cyclotron resonance mass spectrometry. For certain
clusters, depending on both charge state and size, efficient catalytic conversion of CO and N2O
to CO2 and N2 is observed. If N2O is present in sufficient excess, the catalytic cycle shown in
Figure 1 for Pt7 + is running continuously. Poisoning occurs by adsorption of several CO
molecules, and can be suppressed by increasing the N2O pressure in the ICR cell. All clusters
containing more than five platinum atoms readily adsorb CO, while the reactivity with N2O is
strongly size-dependent [1]. Efficient catalytic conversion of CO is observed only for those
clusters which react efficiently with N2O [2].
Figure 1. Catalytic cycle of CO oxidation with N 2O on Pt 7 + as a catalyst. Pt7 + , Pt7O + , Pt 7O 2 + as well as Pt7CO + are
active species in the catalytic cycles. Upon addition of a second CO molecule to Pt 7CO + , the efficiency of the
oxidation reaction is significantly reduced, additional CO molecules poison the cluster. CO adsorption stops when
Pt 7CO 10 + is reached.
References
[1] I. Balteanu, O. P. Balaj, M. K. Beyer, V. E. Bondybey, Phys. Chem. Chem. Phys. 6, 2910 (2004).
[2] O. P. Balaj, I. Balteanu, T. T. J. Roßteuscher, M. K. Beyer, V. E. Bondybey, Angew. Chem. in
print.
25

26
Cluster Reactions and Properties: Laying the Foundation for Cluster
Assembled Materials
A. W. Castleman Jr.
Departments of Chemistry and Physics, Penn State University, University Park, PA 16802
Currently, there is extensive interest in systems of finite size as they often give rise to
unique properties that differ from those of an extended solid or the individual molecular
constituents of which they are comprised. Particularly interesting are nanoscale systems whose
composition can be selectively chosen, and ones whose individual characteristics can be
retained when assembled as an extended material. A major long-term goal of our research in this
area is to develop ways of tailoring the design and formation of new nanoscale materials of
chosen electronic and catalytic properties. Recent success has been obtained in producing alloy
cluster species of specific size and composition that simulate various elements of the periodic
table.
As a complementary approach to conventional surface studies widely used in the field of
catalysis, it is becoming increasingly recognized that cluster science can help elucidate the
physical and chemical properties of condensed phase catalysts and, can provide detailed
information on the mechanisms of reactions and the nature of various reaction sites that enables
certain catalytic materials to be especially effective. In addition, the possible direct use of
clusters as catalysts has aroused interest due to the difference in reactivities often observed for
nanoscale materials compared to conventional bulk catalysts. Our latest findings on mass
selected transition metal oxides, carbon containing, and metallic clusters will be presented. In
related studies, we are employing femtosecond pump-probe techniques to explore the electronic
properties of the clusters, including their excitation and relaxation behavior, which is providing
insights into their evolving band structure. Findings pertaining to the electronic characteristics
of metal-carbon systems and efforts to obtain deposits of mass selected species will also be
discussed.

Melting, Pre-melting, and Glass Transitions in Gallium and Aluminum
Clusters
G.A. Breaux, B. Cao, C.M. Neal, and M. F. Jarrold
Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405-
7102, USA
The melting of gallium and aluminum clusters with between 10 and 70 atoms has been
examined using multicollision induced dissociation (MCID) calorimetry measurements and high
temperature ion mobility measurements. A first order melting transition is indicated by a spike
in the heat capacity due to the latent heat and an abrupt change in the average collision cross
section due to a change in the volume or shape of the cluster when it melts. For some aluminum
clusters (e.g. Al51 + and Al52 + ) the peaks in the heat capacity are bimodal suggesting the presence
of a pre-melting transition where the surface of the cluster melts before the core. While premelting
transitions are present in many simulations of cluster melting, this is the first time they
have been observed experimentally. For some gallium clusters, the collision cross sections
suggest that a melting transition occurs while there is no peak in the heat capacity. This is the
signature for a glass transition which has been predicted to occur for some cluster sizes in
several recent simulations. A glass transition occurs for clusters which are intrinsically
amorphous - clusters that do not have a well-defined geometry.
27

Phase Transition and Phase Coexistence in Atomic Clusters and Other
Mesoscopic Systems
28
Mihai Horoi, Koblar Alan Jackson
Department of Physics, Central Michigan University, Mount Pleasant, Michigan 48859, USA
We investigate signatures of shape transition and shape coexistence phases in small atomic
clusters and other mesoscopic systems, such as the atomic nuclei. One of the best know example
is the prolate-compact shape transition/coexistence phenomena observed in the mobility
experiments of Si clusters.[2] Using a hierarchical strategy that features an extensive tightbinding-based
search of the energy surface, followed by a full density functional theory
investigation of the most stable structures, we have determined the lowest-energy clusters across
the range n=2 to 28.[3] The calculated properties of these clusters are in very good agreement
with available measurements of dissociation energies, ionization energies and ion mobilities,
providing strong evidence that these structures are the ones found in experiments. The
calculations clearly exhibit a transition in the relative stability of prolate and compact clusters
between n=25 and 26, coinciding exactly with the experimental behavior. The lowest energy
prolate and compact structures are found almost degenerate, justifying the coexistence of shapes
observed in the experiment. The binding energy per atom of the ground states vs N -1/3 exhibits a
long plateau in the transition/coexistence region (see Fig.), suggesting that this phenomena may
be related to a relative soft surface tension. Similar behavior was recently found in the isotope
152 of the nucleus of the element Sm, for which the ground sate, J π = 0 + , is known to be very
deformed (oblate), and the first excited J π = 0 + , is compact. A similar signature in the binding
energy per atom of the Sm isotopes can also be extracted from the available experimental data.
Figure 1. Shape transition and shape coexistence signature in the binding energy per atom of Si clusters. Figure taken
from Ref. [1], but red dots are the results of our simulations (Ref. [3]).
References
[1] T. Bachels and R. Schaefer, Chem. Phys. Lett. 324, 356 (2000).
[2] R.R. Hudgins, I. Motoharu, and M.F. Jarrold, J. Chem. Phys. 111, 7865 (1999).
[3] A.K. Jackson, M. Horoi, I. Chaudhuri, Th. Fraunheim, and A. A. Shvartsburg, Phys. Rev. Lett. 93,
013401 (2004).

Vibrational Spectroscopy of Large Sodium Doped Water Clusters:
Size Selection by Ionization-Vibration Coupling
Christof Steinbach, Udo Buck
Max-Planck-Institut für Strömungsforschung, Bunsenstrasse 10, 37073 Göttingen, Germany
One way to solve the problem of measuring reliable size distributions of weakly bound
clusters is to dope the clusters with one sodium atom and to ionize the system by a single
photon close to the threshold. 1,2 In this contribution we have extended this method to obtain
complete size selection. This is achieved by coupling the UV radiation of a dye laser below the
ionization threshold with the tunable infrared radiation of an optical parametric oscillator. The
procedure works provided that there is sufficient coupling between the vibrational and the
electronic motion of the ionization.
We have applied this method to the measurement of the vibrational OH-stretch spectra of
Na(H2O)n clusters in the size range from n=8 to 80. The spectra are dominated by intensity
peaks around 3400 cm -1 which we attribute to an increased transition dipole moment of
delocalized electrons which have been observed in calculations for this type of clusters. 3 The
spectral features are discussed and compared with those obtained for pure water clusters 4 and
water clusters doped with sodium ions. 5
References
[1] S. Schütte and U. Buck, Int. J. Mass. Spectrom. 220, 183 (2002).
[2] C. Bobbert, S. Schütte, C. Steinbach, and U. Buck, Eur. Phys. J. D Journal 19, 183 (2002).
[3] C. J. Mundy, J. Hutter, and M. Parrinello, J. Am. Chem. Soc. 122, 4837 (2000).
[4] C. Steinbach, P. Andersson, J. K. Kazimirski, U. Buck, V. Buch, and T.A. Beu,
J. Phys. Chem. A 108, 6165 (2004).
[5] F. Schulz and B. Hartke, Phys. Chem. Chem. Phys. 5, 5021 (2004).
29

30
Novel elongated Chevrel-type (Mo3S3)nS2 clusters
Gotthard Seifert and Sibylle Gemming
Institut f. Physikalische Chemie, Technische UniversitätDresden, D-01062 Dresden, Germany
Clusters of the composition Mo3nS3n+2 can be regarded as building blocks of the
corresponding sulfur-based Chevrel phases [1]. These compounds are generally built from equal
amounts of two Mo3nS3n+2 species with different values of n, thus the overall formula unit of the
network is Mo3nS3n+4. For the alkali metals as counter ions the charge state of the single cluster
building block is -1. Thus, the clusters in these compounds occur in the same charge state as the
free clusters recently observed by experimental studies [2].
The cluster series up to n = 9 was investigated by density-functional-based calculations. Both
the neutral and the anionic species were investigated. All structures up to Mo21S23 exhibit a
HOMO-LUMO gap of about 0.5 eV. The relative stability of the neutral clusters shows a weak
even-odd-alternation, which roughly correlates with the HOMO-LUMO spacings. The relative
stabilities of the different members of the cluster sequence are highly dependent on the charge
state, i.e. on the number and type of counter ions in a solid phase. For comparison the infinitely
long [Mo6S6] n chain was investigated by DFT band structure calculations, employing periodic
boundary conditions.
Calculated I-V curves fur such clusters show that the quasi one-dimensional Chevrel-type
structures are promising candidates for nanoelectronic devices.
Figure 1. Chevrel type structures of the Mo6S8 , Mo9S11 , Mo18S20 clusters and part of an infinite chain of a Chevrel
structure (left to right, black Mo atoms ).
References
[1] D. Salloum, R. Gautier, P. Gougeon, M. Potel, J. Solid. State Chem. 177, 1672 (2004).
[2] N. Bertram , Y.D. Kim, G. Ganteför, to be published

Novel Properties of Soft-Nano-Molecular Clusters
Koji Kaya 1 , Atsushi Nakajima and Masaaki Mitsui 2
1 Discovery Institute, RIKEN, Wako, 351-0198 Saitama, Japan
2 Department of Chemistry, Keio Uinversity, Hiyoshi, Yokohama, Japan
Over the past 20 years, our group at Keio University has devoted to the development of
new material science in nao-size regime on the basis of small molecules and metal atoms.
Several new findings have been already reported. However , these reports have been restricted
to relatively small size clusters with mass number less than several hundreds. Recently we have
succeeded in the synthesis of relatively large sized molecular clusters of aromatic molecules
such as benzene, naphthalene and anthracene. From the photoelectron spectra of anion clusters
of these molecules as shown in the figure, we found peculiar behavior of the clusters in the mid
size range where ordered and disordered electronic properties coexists. We will discuss this
subject.
Then, discussin will extends to the post nanoscience project which will be conducted under the
collaboration of several national organizations including RIKEN. The project focuses attention
on the synthesis and understanding the mechanism of novel bio-miemetic materials by the
collaboration among chemists, bio-scientists and information physicists.
Photoelectron Spectra of Size Selected Anthracene Cluster
Anions
II
I
II
I
31

32
Melting of Sodium Clusters: Where Do the Magic Numbers Come
from?
H. Haberland, T. Hippler, J. Donges, O. Kostko, M. Schmidt, and B. v. Issendorff
Fakultät für Physik, Universität Freiburg, H.Herderstr. 3, 79104 Freiburg, Germany
Melting temperatures of Na clusters show size-dependent fluctuations that have resisted
interpretation so far. It will be discussed that these temperatures, in fact, cannot be expected to
exhibit an easily understandable behavior. The energy and entropy differences between the
liquid and the solid clusters turn out to be much more relevant parameters. They exhibit
pronounced maxima that correlate well with geometrical shell closings, demonstrating the
importance of geometric structure for the melting process. Icosahedral symmetry dominates, a
conclusion corroborated by new photoelectron spectra measured on cold cluster anions. In the
vicinity of the geometrical shell closings the measured entropy change upon melting is in good
agreement with a simple combinatorial model.

Posters
33

Carbon
35

Structure and Bonding in Carbon Clusters C14 to C60
Jeongeon Park, Jihye Shim, and Eok Kyun Lee
Department of Chemistry, Korea Advanced Institute of Science and Technology, 373-1, Guseong-dong,
Yuseong-gu, Deajeon, 305-701, Republic of Korea
B - 1
Density functional calculations have been applied to study various isomers of neutral carbon
clusters C2n( 7 ≤ n ≤ 30 ) using both local spin density and generalized gradient approximations
for the exchange-correlation energy. The structures of stable isomers include chains, rings,
cages, and graphitic structures. We examined the most stable structure for each cluster of
various size and found a specific tendency as the size changes. Cage structure is the most stable
structure for n≥16. We observed a fourfold periodicity in the monocyclic ring structures. Small
effect of spin-polarization was observed in the monocyclic rings and the graphitic isomers with
n = 4k( k = 1, 2, 3, ....). We calculated the ionization energy and the cohesive energy for the
cage structures, and compared with previous results. All structures have been fully relaxed by ab
initio molecular dynamics combined with simulated annealing, and the change of the
trajectories of each atomic coordinate during the structure relaxation has been recorded . We
further examined the characteristic features of the electronic structure of each isomer.
References
[1] R.O. Jones and G.Seifert, Phys. Rev. Lett. 79, 443 (1997).
[2] G. Seifert, K. Vietze and R. Schmidt, eJ. Phys. B: At. Mol. Opt. Phys. 29, 5183 (1996).
37

38
B - 2
High Resolution Measurements of Fullerenes and Endohedrals
K. Głuch 2 , S. Matt-Leubner 1 , S. Feil 1 , O. Echt 3 , C. Lifshitz 4 , S. Denifl 1 , S. Ptasinska 1 , B. Concina 5 , P.
Scheier 1 , and T. D. Märk 1
1 Institut für Ionenphysik, Leopold Franzens Universität, A-6020 Innsbruck Austria
2 Institute of Mathematics, Physics and Informatics Marie Curie-Sklodowska University, Lublin, Poland
3 University of New Hampshire, Durham, New Hampshire, USA
4 The Hebrew University of Jerusalem, Jerusalem, Israel
5 Department of Physics and Astronomy, University of Aarhus, Denmark
The stability of fullerenes has been a controversial topic for some time. The (adiabatic)
dissociation energies for the preferred dissociation reactions of isolated (gas-phase) fullerenes
Cn → Cn-2 +C2 cannot be derived from measured thermodynamic quantities, not even for n = 60
or 70. There is also a growing interest in fullerenes of sizes larger and smaller than C60 and C70.
We have measured the kinetic energy released in the unimolecular dissociation of fullerene ions,
Cn+ → Cn-2+ + C2, for sizes 42 ≤ n ≤ 90 [1]. A three sector field mass spectrometer equipped
with two electrostatic sectors has been used in order to ensure that contributions from
isotopomers (same n but containing 13C) do not distort the experimental kinetic energy release
distributions. We apply the concept of microcanonical temperature to derive from these data the
dissociation energies of fullerene cations. They are converted to dissociation energies of neutral
fullerenes with the help of published adiabatic ionization energies. The results are compared
with literature values.
The fascinating possibility of caging atoms was noticed immediately by Kroto et al when they
proposed the hollow icosahedral structure of C60. The kinetic stability of endohedrals under
ambient conditions has originally presented some puzzles. We have measured the kinetic energy
release distributions for unimolecular C2 loss from singly and multiply charged Sc3N@C78z+
(z=1,2) and Sc3N@C80z+ (z=1,2,3) [2]. Using finite heat bath theory we have deduced the
dissociation energies of these endohedral ions toward loss of C2. The data show that the
complexation energies i. e. the adiabatic binding energies between Sc3N and the fullerene cage
Cnz+ are, for a given charge state and within the experimental uncertainty, identical for n = 76,
78 and 80.
Formation of negative fullerene ions, especially of C60–, has been a contentious issue over the
last decade. We try to clarify the mystery of the zero energy peak of the negative C60 with the
help of a specially dedicated electron monochromator instrument. Moreover we compare for the
first time experimental data of negative empty cage fullerenes and endohedrals.
References
[1] K. Gluch, S. Matt Leubner, O. Echt, B. Concina, P. Scheier, and T.D. Märk, High-resolution
kinetic energy release distributions and dissociation energies for fullerene ions Cn+, 42

Photoelectron Spectroscopy of Fullerene Dianions C76 2- , C78 2- and C84 2-
Oli T. Ehrler 1 , Filipp Furche 2 , J. Mathias Weber 1 , and Manfred M. Kappes 1
B - 3
1 Institut für Physikalische Chemie mikroskopischer Systeme, Universität Karlsruhe (TH), Kaiserstrasse
12, Karlsruhe, D-76128, Germany
2 Institut für Physikalische Chemie, Theoretische Chemie, Universität Karlsruhe (TH), Kaiserstrasse 12,
Karlsruhe, D-76128, Germany
In the past years, investigations of multiply negatively charged anions (MCAs) have
become a research field of their own. MCAs should obey a particular high degree of electron
correlation to minimize Coulomb repulsion between the excess charges, which are no longer
screened due to the overall neutral core and are thus an interesting benchmark system for
theoretical chemists. Moreover, long-range Coulomb interaction between an outgoing electron
and the still negatively charged core leads to a significantly different photodetachment threshold
law than Wigner’s law for monoanions due to the formation of the repulsive Coulomb barrier
(RCB), which can kinetically hinder the decay of excited MCAs and even stabilize metastable
MCAs with respect to electron emission.
Due to their high symmetry and available wide size distribution maintaining a similar
morphologic pattern, multiply negatively charged fullerenes are a particularly suitable target to
study size evolution effects in MCAs. In the present work [1,2], we report laser photoelectron
spectra of the doubly negatively charged fullerenes C76 2- , C78 2- and C84 2- at 2.33 eV, 3.49 eV, and
4.66 eV photon energy. From these spectra, second electron affinities and vertical detachment
energies, as well as estimates for the RCBs are obtained. These results are discussed in the
context of electrostatic models. They reveal that fullerenes are similar to conducting spheres,
with electronic properties scaling with their size. The experimental spectra are compared with
the accessible excited states of the respective singly charged product ions calculated in the
framework of time dependent density functional theory (TDDFT).
Figure 1. Size dependence of AEA 2 values for fullerenes.
Black squares: Spectroscopic data with experimental uncertainty. Open squares/circles: upper/lower limit for AEA 2
(fully correlated point charges, dielectrically shielded vs. uncorrelated delocalized charges, w/o dielectric shielding);
open triangles: AEA2 values obtained from a scalable model (see [1]).
References
[3] O.T. Ehrler, J.M. Weber, F. Furche, and M.M. Kappes, Phys. Rev. Lett. 91, art. no. 113006 (2003).
[4] O.T. Ehrler, F. Furche, J.M. Weber, and M.M. Kappes, J. Chem. Phys. — accepted.
39

40
B - 4
Radiative Cooling of Fullerenes and Endohedral Fullerenes
Martin Hedén, Fredrik Jonsson, Elin Rönnow, Andrei Gromov, Klavs Hansen, Eleanor E. B. Campbell
Department of Physics, Göteborg University, SE-41296 Göteborg, Sweden
One of the interesting properties of the fullerenes is that, due to the similarity between their
binding energies and ionisation potentials, excited molecules have decay channels in which the
neutral fragmentation competes with delayed ionisation. An additional competing channel is
that of radiative decay. In order to be able to extract reliable information from experiments
concerning the binding energies of the molecules it is essential to understand the various
competing mechanisms and have a consistent picture of the behaviour of these highly excited
molecules. In this presentation we return to the determination of the radiative cooling of
fullerene ions as determined by time-of-flight experiments [1]. We compare the extracted
product of emissivity and dissociation energy from experiments in which the starting molecule
is different. In particular, we were interested in comparing the emissivity of an endohedral
fullerene (in this case La@C82) with empty fullerenes. The data is displayed in Fig. 1 and
compared with earlier data from C60 and more recent data from the Århus group [2]. Rather
good agreement is obtained between the different data sets for the small fullerenes with a
substantially higher scatter in the points for the larger molecules. However, we note that there is
no significant difference in the emissivity of the endohedral fullerene compared with that of the
empty fullerenes. The experimental details and assumptions will be presented and results will be
discussed in the context of a simple model to describe the radiative cooling.
εD 3
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
40 44 48 52 56 60 64 68 72 76 80 84
Figure 1. Product of emissivity and the cube of the dissociation energy, extracted from time-of-flight data for
different parent molecules. The full squares are data obtained from C60, C70 or C84 starting molecules. The empty
squares are starting from La@C82. Full circles are early data from [1]. Empty circles are extracted from data given
by [2].
References
[1] K. Hansen and E.E.B. Campbell, J. Chem. Phys., 104 5012 (1996).
[2] S. Tomita et al., Phys. Rev. Lett. 87 073401 (2001)
N

Nucleation of single-walled carbon nanotubes on catalyst particles:
MD and electronic structure calculations
Arne Rosén 1, 1, 2
, Feng Ding and Kim Bolton
1 Experimental Physics, School of Physics and Engineering Physics, Göteborg University and Chalmers
University of Technology, SE-412 96, Göteborg, Sweden
2 School of Engineering, University College of Borås, SE-50190, Borås Sweden
B - 5
Metal catalyzed single-walled carbon nanotube (SWNT) nucleation was studied by classical
molecular dynamics (MD) and electronic structure theory. The simulations revealed the atomiclevel
mechanism for SWNT nucleation on metal catalyst particles. The SWNTs nucleate
between 800 - 1400 K, [1] which is the same temperature interval used for chemical vapor
deposition (CCVD) experiments. Also, in agreement with experimental results the nucleated
SWNT has the same diameter as the catalyst particle [2]. The studies also show that a highly
supersaturated carbon concentration in the catalyst particle is needed to initiate the nucleation
process. [1] Based on the simulations a detailed Vapor-Liquid-Solid (VLS) growth model was
developed for both liquid and solid catalyst particles. [1, 3] Furthermore, MD and electronic
structure theory studies indicate that the catalyst particle must be able to maintain an open end
of the growing SWNT in order to be suitable for growth.
References:
[1] F. Ding, K. Bolton and A. Rosén, J. Phys. Chem. B, 108, 17369-17377 (2004).
[2] F. Ding, A. Rosén, and K. Bolton, J. Chem. Phys. 121, 2775-2779 (2004).
[3] F. Ding, A. Rosen, and K. Bolton, Chem. Phys. Lett. 393, 309-313 (2004).
41

42
B - 6
Sphere currents in fullerenes
Mikael P. Johansson, Dage Sundholm, Jonas Jusélius, Juha Vaara
Department of Chemistry, University of Helsinki, P. O. Box 55, FI-00014 Helsinki, Finland
We investigate the magnetically induced electric currents in fullerenes, using the newly
developed GIMIC methodology [1]. With GIMIC, a quantitative measure of the current
strengths can, for the first time, be obtained. A remarkable difference between neutral
Buckminsterfullerene and its spherically aromatic [2] +10 cation is revealed. In both, uniform
three-dimensional currents, circling the fullerenes are induced. In C60, these sphere currents are
oppositely directed; the exohedral diamagnetic and endohedral paramagnetic currents to a large
extent cancel, resulting in global non-aromaticity. C60 10+ , on the other hand, supports a
unidirectional, global diamagnetic current of significant strength, consistent with spherical
aromaticity. These global sphere currents should be considered the defining feature of
aromaticity in fullerenes [3]. The stabilising effect of spherical aromaticity is discussed in
connection with the recently postulated all-golden fullerene, Au32 [4]. Spherical aromaticity is
found to be of crucial importance for the stability of the species.
References
Figure 1. From left to right: Au 32; sphere currents; C 60.
[1] J. Jusélius, D. Sundholm, J. Gauss, "Calculation of current densities using gauge-including atomic
orbitals", J. Chem. Phys. 121, 3952 (2004).
[2] A. Hirsch, Z. Chen, H. Jiao, "Spherical Aromaticity in Ih Symmetrical Fullerenes: The 2(N+1) 2
Rule", Angew. Chem. Int. Ed. 39, 3915 (2000).
[3] M. P. Johansson, J. Jusélius, D. Sundholm, "Sphere Currents of Buckminsterfullerene", Angew.
Chem. (in press).
[4] M. P. Johansson, D. Sundholm, J. Vaara, "Au32: A 24-Carat Golden Fullerene", Angew. Chem. Int.
Ed. 43, 2678 (2004).

Chemistry
43

Gold cluster molecular surface chemistry
André Fielicke 1 , Gert von Helden 1 , Gerard Meijer 1 , David B. Pedersen 2 , Benoit Simard 2 and
David M. Rayner 2
B - 7
1 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
2 Steacie Institute for Molecular Sciences, National Research Council, 100 Sussex Drive, Ottawa, Ontario
K1A 0R6, Canada
The chemistry of gold nanoparticles is an important example of the fundamental difference
between material in its bulk and in its cluster forms. Whereas bulk gold is chemically inert,
deposited gold nanoparticles and clusters have a highly size-specific catalytic activity. A
dramatic size-dependence in reactivity and catalytic turnover has even been found for isolated
gold clusters containing only a few atoms.
We are working to characterize prototypical reactions on free metal clusters in the gas phase.
The intention is to provide a basis for understanding the chemistry of supported nanoparticles.
Our approach is to monitor the independent adsorption, co-adsorption and reaction of relevant
reaction partner molecules on size-selected clusters using infrared multi-photon depletion
spectroscopy with a free electron laser. Our ultimate goal is to obtain thermodynamic
information on cluster surface reactions through variable temperature studies.
Here we discuss progress towards this goal, concentrating on gold clusters. We report on the
interaction of carbon monoxide, CO, and nitric oxide, NO, with cationic and anionic gold
clusters. Successive adsorption of CO molecules on the Aun+ clusters proceeds until a cluster
size specific saturation coverage is reached. Structural information for the bare gold clusters is
obtained by comparing the saturation composition with the number of available equivalent sites
presented by candidate structures of Aun+. Our findings are in agreement with the planar
structures of the Aun + cluster cations with n < �7 suggested by ion mobility experiments
combined with DFT calculations [1]. By inference we also establish the structure of the
saturated Aun(CO)m + complexes. In certain cases we find evidence that successive adsorption of
CO can distort the metal cluster framework. The vibrational spectra of the Aun(CO)m+
complexes in both the CO stretching region and in the region of the Au-C stretch and the Au-C-
O bend add further support to aid in the Aun+ structure determination, provide information on
the structure of the CO complexes and allow comparison with CO adsorbates on deposited
clusters or surfaces.
For Aun- anions we find the same CO uptake patterns reported previously [2]. There is no clear
correlation with geometric structure. Vibrational spectroscopy in the CO stretching region
confirms molecular adsorption of CO, discounting the proposal that CO molecules might react
together to form “glyoxylates” on the surface of Aun - [2].
Nitric oxide absorption on Aun + shows similar uptake patterns to CO for small clusters, but NO
absorbs less readily on clusters with n > 8. Vibrational spectroscopy shows that NO absorbs
molecularly on Aun+ at 300 K. Aun+ is the first cluster system on which we have been able to
find this direct evidence for molecular absorption of NO. The NO stretching frequency, ν(NO),
is consistent with atop NO bonding in a bent configuration but shows a pronounced odd-even
shift that we reproduce by DFT calculations. Finally, preliminary experiments on co-adsorbed
CO and NO show that there is no reaction between CO and NO on Aun + clusters at 300 K.
References
[1] S. Gilb, P. Weis, F. Furche, R. Ahlrichs and M.M. Kappes, J. Chem. Phys. 116, 4094 (2001).
[2] W.T. Wallace and R.L.Whetten, J. Phys. Chem. B 104, 10964 (2000).
45

46
B - 8
Triplatinum carbonyl complexes: preference for terminal sites and
chiral structures
Timo Santa-Nokki and Hannu Häkkinen
Department of Physics, Nanoscience Center, University of Jyväskylä, Finland
We present a systematic density functional theory (DFT) study on the structures of
triplatinum carbonyls Pt3(CO)x q with x=1-6 and q=0,-1. The calculations are able to fully
reproduce and explain the experimentally observed anomalous behaviour in the binding energy
of the ligands in anionic cluster carbonyls by Grushow and Ervin, 1 with the three first ligands
strongly bound (by 220-275 kJ/mol per ligand), the fourth and fifth ligand weakly bound (by
135 kJ/mol), and the sixth ligand again stronger bound (by about 200 kJ/mol). The first three
ligands bind in a tilted configuration at terminal sites in the plane of the triangular platinum
core, making the half-saturated Pt3(CO)3 - a chiral complex. We discuss the relative preference of
terminal and bridge adsorption sites for CO in Pd, Pt, and Au cluster carbonyls in terms of the
strength of the relativistic effects in the metal-carbon bond. We also discuss the implications of
the current work regarding design of bimetallic Au-Pt cluster nanocatalysts for CO oxidation. 2
Figure 1. Sequential binding energy of CO ligands to anionic platinum cluster carbonyls Pt 3(CO) x - for x=1-6. The
DFT results of this work are compared to TCID and PD data from Ref. 1. A conservative estimate for the accuracy of
the theoretical values is ±10 kJ/mol. For each x we also show the ground state structure of the anionic cluster
carbonyl.
References
[1] A. Grushow and K.M. Ervin, J. Am. Chem. Soc. 117, 11612 (1995); A. Grushow and K.M. Ervin,
J. Chem. Phys. 106, 9580 (1997); K.M. Ervin, Int. Reviews in Physical Chemistry 20, 127 (2001).
[2] T. Santa-Nokki and H. Häkkinen, submitted.

Who probes whom: Early transition metal cluster ions meet
(non)aromatic hydrocarbon molecules
Britta Pfeffer, Stephanie Wies, Anita Lagutschenkov, Jens Brück, Matthias Vetter, Tobias Pankewitz,
Gereon Niedner-Schatteburg
TU Kaiserslautern, Fachbereich Chemie, Erwin-Schrödinger-Str. 52, 67663 Kaiserslautern, Germany
B - 9
As already known form former studies [1-4] benzene as well as common olefines react with
niobium cluster cations through complete dehydrogenation. In contrast to other cluster sizes the
Nb19 + cluster is the only one which exclusively binds the aromatic hydrocarbon molecule by
intact adsorption. This exception can also be observed in the reaction with naphthalene (also a
homoaromatic molecule).
In the present work we focus on the difference in reactivity of homoaromatic and of
heteroaromatic systems (benzene, quinoline, naphthaline, pyridine, furan and thiophene).
The data allow for tentative conclusions on the prevailing coordination geometries (parallel or
perpendicular to “cluster suface”). The correspondence of cluster to bulk surfaces will be
discussed.
References
[1] J. Chem. Phys. 102 (12), 4870-4884 (1995).
[2] .J. Phys. Chem. 99 (42), 15497-15501 (1995).
[3] J. Chem. Phys. 108 (13), 5398-5403 (1998).
[4] J. Chem. Phys. 262 (1), 143-149 (2000).
47

B - 10
48
Structural and Electronic Properties of (HAlO)n Clusters
Yi Dong and Michael Springborg
Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrücken, Germany
The structure of (HAlO)n clusters was optimized for n up to 26 using our own 'Aufbau'
approach and for n up to 18 using a genetic-algorithms approach together with a parameterized
density-functional method. The two set of results for (HAlO)n from the 'Aufbau' and the geneticalgorithms
approaches are very close, proving that our two unbiased approaches are reliable.
The shape of the clusters as well as so-called similarity functions, stability functions are
presented in order to analysing the structural properites of the (HAlO)n clusters. Subsequently,
we also study the properties of two interacting clusters that were optimized by the 'Aufbau'
approaches in order to study the marcroscopic, nanoscaled HAlO material that is produced in
experiment.

Efficient Low-Temperature Oxidation of Carbon-Cluster Anions by
SO2: Atmospheric Soot and Health Implications
B - 11
Andrew J. Leavitt 1,2 , Richard B. Wyrwas 2 , William T. Wallace 2+ , Daniel Serrano 1 , Melissa G. Arredondo 2 ,
Farooq A. Khan 1 , and Robert L. Whetten 2*
1 Department of Chemistry, State University of West Georgia, Carrollton, GA 30118.
2 School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA 30332-0400.
+Current address: Department of Chemistry, Texas A&M University, College Station, TX 77842-30012
*Author to whom correspondences should be addressed.
Carbon-cluster anions, CN - , are very active toward SO2 (sticking probability of 0.023 ±
0.005 for C27 - at 25 o C), as compared to their inertness toward other common atmospheric gases
and pollutants. In atmospheric-pressure, fast-flow-reactor experiments at ambient temperature,
primary adsorption of SO2 by the carbon cluster anions, N = 4 – 60, yields CNSO2 - (αN) or CN-
1S - (βN), with neutral CO2, as also detected in collision-induced dissociation. At higher
temperatures, the reaction of SO2 with nascent carbon clusters yields the αN, βN, and CN-1SO -
(γN) along with undetected CO2 and CO. The size-dependent initial reactivity reflects the
previously established cluster structural transitions, i.e. from linear-chain to cyclic to cage
structures. Secondary adsorption is also observed, with higher intrinsic reactivity, suggesting an
accelerating oxidation process. Such carbon clusters serve as model compounds for blackcarbon
soot, as they are formed in sooting flames and can act as nuclei for the formation of
primary soot particles, which also share the local structural features of active soot particle sites.
These findings may therefore have implications for understanding the health and environmental
effects attributed to the coincidence of soot and SO2.
49

B - 12
50
Size Dependent Carbon Monoxide Adsorption on
Neutral Gold Clusters
Nele Veldeman 1 , Peter Lievens 1 , Mats Andersson 2
1 Laboratorium voor Vaste-Stoffysica en Magnetisme, K.U.Leuven,
Celestijnenlaan 200D, B-3001 Leuven, Belgium
2 Department of Experimental Physics, Chalmers University of Technology and
Göteborg University, SE-412 96 Göteborg, Sweden
In spite of gold being chemically inert as bulk material, supported nanosize gold clusters are
found to show a remarkable catalytic activity for many reactions. Among these are CO
combustion, NOx reduction, methanol synthesis and water-gas shift [1]. In order to clarify the
catalytic behaviour shown by small gold particles supported on metal oxides, a number of
studies on deposited clusters, mainly focussing on the size and support dependence, have been
performed [2,3]. Although the substrate often plays an important role, also the investigation of
chemical reactivity and catalytic activity of gas phase clusters is of great importance, as they
may provide deeper insight in mechanisms of reaction processes. In this respect attention so far
is especially drawn to reactivity and catalytic activity [4,5,6,7,8] of ionic gas phase gold
clusters. As a complete understanding of the mechanisms involved in heterogeneous catalysis
by nanoscale gold particles still remains a challenge, extended knowledge gained by reactivity
experiments on neutral gas phase gold clusters towards reactants of interest could be very
helpful.
We report on experiments probing the reactivity of neutral Aun clusters, n=10-65, with CO gas.
The gold clusters are produced in a pulsed laser vaporization cluster source [9], operated at
room temperature (RT) or at liquid-nitrogen temperature (LNT), pass through a low-pressure
reaction cell containing CO gas, and are subsequently laser ionised. The reaction probabilities
are determined by recording mass abundance spectra with time of flight mass spectrometry.
The main observations can be summarized as follows. (i) Upon cooling of the cluster source to
LNT, the reactivity increases substantially. At LNT, the reaction probabilities for Aun with the
first CO molecule are about a factor ten higher than at RT. Moreover, adsorption of two, three
and even four CO molecules is observed, in contrast to RT clusters which at most adsorb one
CO molecule. (ii) The reactivity is found to exhibit strong variations with cluster size, similar at
both temperatures. The observed reaction probabilities yield evidence for electronic properties
governing the size dependence: counting the number of delocalised electrons in reacted species
reveals a correlation between reactivity and cluster electronic shell closings, and odd-even
staggering in the reaction probabilities as a function of the number of atoms is observed.
References
[1] G.C. Bond and D.T. Thompson, Catal. Rev.-Sci. Eng. 41, 319 (1999)
[2] M. Haruta, Catal. Today 36, 153 (1997)
[3] A. Sanchez et al., J. Phys. Chem. A 103, 9573 (1999)
[4] H. Häkkinen and U. Landman, J. Am. Chem. Soc. 123, 9704 (2001)
[5] W.T. Wallace and R.L. Whetten, J. Am. Chem. Soc. 124, 7499 (2002)
[6] J. Hagen et al., Phys. Chem. Chem. Phys. 4, 1707 (2002)
[7] I. Balteanu et al., Phys. Chem. Chem. Phys. 5, 1213 (2003)
[8] D. Stolcic et al. J. Am. Chem. Soc. 125, 2848 (2003)
[9] M. Andersson et al., J. Phys. Chem. 100, 12222 (1996)

B - 13
Photoelectron spectra of lanthanum oxide clusters: decreasing electron
affinities with increasing number of oxygen atoms
R. Klingeler 1 , G. Lüttgens 1 , P. S. Bechthold 1 , N. Pontius 2 , M. Neeb 2 , W. Eberhardt 2
1 Institut fürFestkörperforschung, Forschungszentrum Jülich, 52425 Jülich, Germany
2 Bessy GmbH, Albert-Einstein-Str. 15, 12489 Berlin, Germany
We present a systematic investigation of the electronic structure of La2On (n=1-6) and
La3Om (m=0-4) using photoelectron spectroscopy of anions (hν = 3.495 eV). For La2O and
La2O2 the experiments are supported by density functional and configuration interaction
calculations. The results for the C2v and the D2h ground state isomers, respectively, are in good
agreement with the experimental data. In contrast to some other metal dimers and trimers we
find as a general trend a decreasing electron affinity with an increasing number of chemisorbed
oxygen atoms.
References
[1] R. Klingeler, G. Lüttgens, N. Pontius, R. Rochow, P.S. Bechthold, M. Neeb, and W. Eberhardt,
Eur. Phys. J. D 9, 263 (1999).
51

B - 14
52
Binding energies of CO and H2O on gold cluster cations
Aun+ (n=1-65): A FT-ICR kinetics study
Marco Neumaier 1 , Florian Weigend 1 , Oliver Hampe 1 , and Manfred M. Kappes 1,2
1 Institut für Nanotechnologie, Forschungszentrum Karlsruhe, D-76021 Karlsruhe, Germany
2 Institut für Physikalische Chemie, Universität Karlsruhe, D-76128 Karlsruhe, Germany
Room temperature CO adsorption on isolated gold cluster cations is studied over a wide size
range (Aun + , 1

The Bonding of CO with Au8: Evidence of Cluster Charging
M. A. Röttgen 1 , A. S. Wörz 1 , K. Judai 1,3 , S. Abbet 1 , J. M. Antonietti 1 , U. Heiz 1 , B. Yoon 2 , and
U. Landman 2
1 Institute of Surface Chemistry and Catalysis, Universität Ulm, 89069 Ulm, Germany
2 Georgia Institute of Technology, School of Physics, Atlanta, Georgia 30332-0430, USA
3 Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan
B - 15
While Gold is inert as bulk material, it becomes catalytically active as nanoscale particles or
clusters supported onto oxide support materials. In the last few years, effort was made to get a
better insight into the relevant reaction mechanisms and to understand this astonishing
phenomenon on a molecular level. For large gold particles a few nanometers in size, it is
discussed on the one hand whether the catalytic activity can be explained by the presence of
active sites on the cluster-support interface or by low-coordinated, highly reactive sites. On the
other hand, for small clusters, the gold octamers bound to F-centers of an MgO surface are the
smallest known gold heterogeneous catalysts able to transform CO into CO2. The key for the
low-temperature conversion on Au8 is the binding of the molecular oxygen and the concomitant
O-O bond activation to a peroxo-like adsorbate state. This is possible as the cluster’s electronic
states show resonance with the 2π* molecular states of oxygen and as these antibonding states
are pushed below the Fermi level of the system upon interaction with the cluster. Interestingly,
the same cluster bound to a terrace site of an MgO surface is inert for the combustion reaction.
Extensive ab initio calculations predicted that charging from the F-center into the cluster is
essential for the activation of gold octamers.
In this contribution, we present new findings showing experimental evidence for this prediction.
The measured CO stretch frequencies, ν(CO), under reaction conditions are red-shifted by about
30-50 cm-1 for the octamer bound to the F-center (Au8/CO/O2/MgO(FC)) in comparison to the
octamer bound to the five-coordinated terrace sites (Au8/CO/O2/MgO(O5c)). Extensive ab
initio calculations reveal that this shift is caused by enhanced backdonation into the antibonding
2π* orbital of CO adsorbed on the Au8/O2/MgO(FC) complex and reveal important details of
the bonding of CO for understanding the backdonation. In addition, calculations on free
Au8/O2/CO complexes indeed show this effect to be related to a substantial change in charging
of the cluster [1].
References
[1] B. Yoon et al., Accepted for Publication in Science (2004).
53

B - 16
54
Reactivity of Size-Selected Gas-Phase Transition Metal Carbide and
Sulfide Clusters
James Lightstone 1 , Melissa Patterson 1 , Robert J. Beuhler 2 1, 2
, Michael G. White
1 Department of Chemistry, Stony Brook University, Stony Brook, NY 11974, USA
2 Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973, USA
We have recently constructed a cluster deposition apparatus which employs a magnetron
sputtering source for generating gas-phase cation clusters of pure metals and metallic
compounds. The focus is on generating clusters of the early transition metal compounds
(carbide and sulfides), which are known in their bulk form to be active catalysts for a wide
range of heterogeneous reactions [1,2]. In many cases, metal carbides offer distinct advantages
over the parent metal in selectivity and resistance to poisoning, and for certain reactions their
catalytic behavior is similar to that of the Group 8-10 noble metals [2,3]. Very recent theoretical
calculations also suggest that small carbide clusters, i.e., the Ti8C12 Met-Car and Ti14C13
nanocrystallite, are more reactive than bulk TiC surfaces [4]. The work reported here examines
the gas-phase reactivity of small transition metal carbide and sulfide clusters as a first step
towards investigations of model catalysts prepared by size-selected deposition.
Ion beams containing a wide array of transition metal compound clusters, TxMy + (T ≡ Ti,
Mo, Zr, Nb; M ≡ C, S), were generated using a magnetron sputtering source, including “magic”
number species such as the Ti8C12 + Met-Car. The gas-phase reactivity of mass-selected TxMy +
clusters was studied using a hexapole collision cell, into which reactive gases were introduced,
and a second quadrupole mass filter for product detection. Results will be presented for the
adduct formation and reactions of the Ti8C12 + Met-Car with a variety of sulfur containing
molecules, such as OCS shown in the accompanying figure below. In addition, we will also
present results on the reactivity of MoxSy + clusters and future plans for size-selected cluster
deposition. This work was supported by the U.S. Department of Energy, Office of Basic Energy
Sciences, Division of Chemical Sciences under contract No. DE-AC02--98CH10886
Figure 1. Mass spectrum of the reaction
products resulting from collisions between
Ti8C 12 + and OCS at 300K. .
References
500 600 700 800 900 1000
[1] J.G. Speight, The Chemistry and Technology of Petroleum, second ed., New York, McGraw-Hill,
1991.
[2] Chen, J. G., Chem. Rev. 1996, 96, 1477; Oyama, S. T., Catal. Today 15, 179 (1992).
[3] Levy, R. L.; Boudart, M., Science 181, 547 (1973).
[4] H. Hou, J. T. Muckerman, P. Liu and J. A. Rodriguez, J. Phys. Chem. 107, 9344 (2003); P. Liu and
J. A. Rodriguez, J. Chem. Phys. 119, 10895 (2003).
Intensity
1.20E-008
1.00E-008
8.00E-009
6.00E-009
4.00E-009
2.00E-009
0.00E+000
Ti 8 C 12
Ti 8 C 12 + S
Ti 8 C 12 + SCO
Ti 8 C 12 + S(SCO) 3
Mass
Ti 8 C 12 + S(SCO) 5

B - 17
Probing Strong Hydrogen Bonds and Cold Metal Oxide Clusters with
Infrared Photodissociation Spectroscopy
Knut R. Asmis
Abteilung Molekülphysik, Fritz-Haber-Institut der Max-Planck-Gesellschaft
Faradayweg 4-6, D 14195 Berlin
In recent years much effort has been aimed at improving the sensitivity and selectivity of
experimental methods to study the vibrational spectroscopy of gas phase ions. Due to the lack of
widely tunable infrared (IR) light sources most of these studies had been limited to the region
above 2400 cm -1 , i.e., the spectral region of hydrogen-stretching motions and of IR-active
combination bands. The application of the infrared free-electron laser FELIX, which generates
tunable radiation in the 40 – 2200 cm -1 region, to molecular spectroscopy by Meijer, von Helden
and coworkers has bridged this gap [1]. We have recently extended their technique to study the
vibrational spectroscopy of mass-selected gas-phase cluster cations and anions at variable
temperature. Application of this technique to two important compound classes will be discussed
and compared to the results of complimentary experiments on mass-selected neutral clusters
using femtosecond pump-probe spectroscopy.
The hydrogen bond interaction is key to understanding the structure and properties of water
and biomolecules. However, our understanding of strong, low-barrier hydrogen bonds and their
central role in enzyme catalysis, biomolecular recognition, proton transfer across biomembranes
and proton transport in aqueous media remains sketchy. We recently measured the first IR
spectra of several prototypical systems, directly probing the shared proton region of the
potential energy surface [2,3]. Our experiments demonstrate that the theoretical description of
the vibrations of strong hydrogen bonds is considerably more complex than originally
anticipated and not yet solved satisfactorily, even for small systems and at the highest levels of
theory currently available.
Transition metal oxides play an increasingly important role in heterogeneous catalysis.
Recent gas-phase reactivity studies on vanadium oxide cluster ions were aimed at understanding
the nature of the reactive sites. The interpretation of the reactivity data requires information on
the structure of the cluster ions. We employ IR photodissociation spectroscopy in combination
with electronic structure calculations to identify the geometric structure as well as structural
trends as a function of cluster size in vanadium oxide cluster cations and anions [4]. For the
cluster anions we present the first experimental evidence for the formation of polyhedral
vanadium oxide cages in the gas phase. The measured IR spectra are sensitive probes for charge
localization of unpaired d-electrons and show a strong resemblance with the IR spectrum of a
V2O5 surface already at medium cluster sizes.
References
[1] G. von Helden, I. Holleman, G. M. H. Knippels, A. F. G. van der Meer, and G. Meijer, Phys. Rev.
Lett. 79, 5234 (1997).
[2] K. R. Asmis, N. L. Pivonka, G. Santambrogio, M. Brümmer, C. Kaposta, D. M. Neumark, and L.
Wöste, Science 299, 1375 (2003).
[3] M. Nee, C. Kaposta, A. Osterwalder, C. Cibrian Uhalte, T. Xie, A. Kaledin, S. Carter, J. M.
Bowman, G. Meijer, D. M. Neumark, and K. R. Asmis, J. Chem. Phys. 121, 7259 (2004).
[4] K. R. Asmis, G. Meijer, M. Brümmer, C. Kaposta, G. Santambrogio, L. Wöste, and J. Sauer, J.
Chem. Phys. 120, 6461 (2004).
55

B - 18
56
Oxygen adsorption at anionic free and supported Au clusters
L. M. Molina 1,2 and B. Hammer 1
1 iNANO and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark
2 Departamento de Física Teórica, Universidad de Valladolid, E-47011 Valladolid, Spain
Recently, much attention has been paid to the catalytic activity of supported Au
nanoparticles and clusters [1]. Both small free unsupported anions [2] and MgO-supported
clusters [3] have been found very active towards CO oxidation. However, sizable differences in
the size-dependent activity are found on each case, which are difficult to explain. In this work,
the structure, stability and O2 adsorption properties of free anionic Aun - (n=1-11) clusters and
negatively charged Aun clusters supported at defected MgO(100) surfaces are investigated using
density functional theory. The free anionic clusters with an even number of atoms readily
adsorb O2 since the excess unpaired electron can be easily transferred to the adsorbate. On the
contrary, Au clusters supported at F + -centers show a much more complex behaviour. They attain
similar electronic structure as the anionic free clusters, but the Madelung potential pins one
electronic orbital to the defect. For large band gap clusters (mainly small clusters, which prefer
2D geometries, see Figure) this is the orbital with the excess electron, which therefore cannot be
transferred to an adsorbate, meaning that O2 adsorbs only weakly. Larger clusters become threedimensional
and more metalic and hence capable of screening the support potential and binding
O2 with charge transfer. This helps to understand why the supported clusters only become active
starting at Au8 [3], whereas free Au6 - has been found to be extremely active [2].
Figure 1. Equilibrium structures for O 2 adsorption at Au n (n=2-11) clusters attached to an F + -center. For n=4-11, the
most representative 2D and 3D Au n isomers are shown. At Au 7-Au 8, a transition from 2D to 3D is found.
References
[1] M. Haruta, Catal. Today 36, 153 (1997).
[2] W. T. Wallace and R. L. Whetten, J. Am. Chem. Soc. 124, 7499 (2002).
[3] A. Sanchez et al., J. Phys. Chem A 103, 9573 (1999).

B - 19
Density Functional Studies Of Noble Metal Clusters. Adsorption Of O2
And CO On Gold And Silver Clusters
Eva M. Fernández 1 , María B. Torres 2 , and Luis C. Balbás 1
1 Dpto. de Física Teórica, Atómica y Óptica, Universidad de Valladolid E-4701 Valladolid, Spain
2 Dpto. de Matemáticas y Computación, Universidad de Burgos E-090006 Burgos, Spain
By means of first-principles density functional calculations, based on norm-conserving
pseudo-potentials and numerical atomic basis sets, we study different noble metal cluster
systems and properties. First, we show that, together with relativistic effects, the type of
exchange-correlation functional (GGA or LDA) is more critic for Au than for Ag or Cu clusters
in order to determine the planar or three dimensional cluster geometry 1 . Second, we find cagelike
stable structures for neutral Au18, Au20, Au32, Au50, and Au162, see fig.1. However, after
adding an extra electron only Au20 - remains cage-like. On the other hand, Ag20 and Cu20 clusters
adopt compact amorphous-like Cs structures. Third, we investigate the element- and sizedependent
electron stability of gold clusters cations doped with a transition metal impurity 2 ,
AunTM + (TM = Sc, Ti, V, Cr, Mn, Fe, Au; n ≤ 9), and we obtain a clear explanation of the
cluster abundance peaks observed recently in photo-fragmentation experiments. Fourth, we
study the size dependent adsorption of Om (m=2,4) molecules on small Agn - anion clusters (3≤ n
≤9), as well as the adsorption of O2 on neutral Aun (5 ≤ n ≤ 10) and anions Aun - (n ≤ 7) clusters.
The adsorption energy of O2 show marked odd even effects in all the cases. For Agn - anions
with odd (even) n, the adsorption of a second O2 molecule increase (decrease) the adsorption
energy of O2. The atomic O on Aun - O is preferable for n ≥ 4 than O2 adsorption. The
dissociative adsorption is spontaneous for neutral gold clusters with n=6,7. For Aun, clusters
with odd number of atoms are more active toward O2 adsorption. The O2 adsorbs preferably on
top of Au atoms, except for Au5, for which a bridge site is favorable, see fig. 2. Fifth, we study
also the size dependent adsorption of CO on small Aun clusters (5 ≤ n ≤ 10). The binding energy
of CO adsorption on Au does not present odd even effects with clusters size. Top position is
preferable for CO adsorption except for n = 5,7. Cluster with n = 5,7 present the biggest binding
energy.
We study also the trend in the bond distances, the vibrational frequencies and Mulliken
population of adsorbed species on gold clusters.
Figure 1. Cage-like and isomeric compact structures for Aun with n = 18, 20, 32, 50 and 162.
Figure 2. O2 adsorption on Aun clusters. * dissociative adsorption. + molecular adsorption.
References
[1] E. M. Fernández, J. M. Soler, I. L. Garzón and L. C. Balbás, Phys. Rev. B 70, 165403 (2004).
[2] M. B. Torres, E. M. Fernández and L. C. Balbás, Phys. Rev. B (submitted).
57

B - 20
Gold Clusters, CO-Chemisorbed Au Clusters, and Binary Au Clusters
58
Xi Li, B. Kiran, H. J. Zhai, Jun Li, Hai-Feng Zhang, and Lai-Sheng Wang
Department of Physics, Washington State University, 2710 University Drive, Richland, WA 99352, USA
and W. R. Wiley Environmental Molecular Sciences Laboratory and Chemical Science Division, Pacific
Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
Gold is a unique element with unusual chemistry due to the strong relativistic effect [1]. We
will present our recent work on small gold clusters [2-4], CO-chemisorbed gold clusters [5], and
novel gold-containing molecules [6-8]. We found previously that Au20 is a highly stable
tetrahedral cluster [2]. Recently, we showed that we can also synthesize the tetrahedral Au20
cluster in solution with phosphine ligands [4]. In experiments aimed at providing insight into the
catalytic effect of nanogold, we studied CO-chemisorbed Au clusters, Aum(CO)n - (m = 2-5; n =
1-7) [5]. The photoelectron data suggest that CO acts as an electron donor to the Au clusters and
provide information about the CO-chemisorption site. This work provides direct experimental
insight into the cooperative chemisorption of CO and O2 onto Au clusters.
Au13 does not have the high symmetry Ih structure [3]. However, a class of stable Ih clusters
containing 12 Au atoms and an impurity atom (M), M@Au12, was predicted to have Ih structures
[9]. We will report our experimental observation and theoretical confirmation of these highly
stable and symmetric gold clusters with M = Mo, W, V, Na, and Ta [6,7]. Finally we will
present our discovery of the novel H-like chemistry of Au in forming the highly stable
aurosilane SiAu4 and other Si-Au clusters in analogy to Si-hydride molecules [8].
References
Td Au20 Au20(PH3)4 Ih M@Au12 Td SiAu4
[1] P. Pyykko, Angew. Chem. Int. Ed. 43, 4412 (2004).
[2] J. Li, X. Li, H. J. Zhai, and L. S. Wang, Science 299, 864-867 (2003).
[3] H. Häkkinen, B. Yoon, U. Landman, X. Li, H. J. Zhai, and L. S. Wang, J. Phys. Chem. A 107,
6168-6175 (2003).
[4] H. F. Zhang, M. Stender, R. Zhang, C. M. Wang, J. Li, and L. S. Wang, J. Phys. Chem. B 108,
12259-12263 (2004).
[5] H. J. Zhai and L. S. Wang, J. Chem. Phys., in press.
[6] X. Li, K. Boggavarapu, J. Li, H. J. Zhai, and L. S. Wang, Angew. Chem. Int. Ed. 41, 4786-4789
(2002).
[7] H. J. Zhai, J. Li, and L. S. Wang, J. Chem. Phys. 121, 8369-8374 (2004).
[8] B. Kiran, X. Li, H. J. Zhai, L. F. Cui, and L. S. Wang, Angew. Chem. Int. Ed. 43, 2125-2129
(2004).
[9] P. Pyykko and N. Runeberg, Angew. Chem. Int. Ed. 41, 2174-2176 (2000).

B - 21
Mass-Selected Infrared Photodissociation Spectroscopy of Vanadium
Oxide Cluster Anions
G. Santambrogio 1 , M. Brümmer 1 , S. Fontanella 1 , L. Wöste 1 , J. Sauer 2 , G. Meijer 3 , and K. R. Asmis 3
1 Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, Berlin, 14195, Germany
2 Institut für Chemie, Humboldt-Universität Berlin, Unter den Linden 6, Berlin, 10099, Germany
3 Abteilung Molekülphysik, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195,
Berlin, Germany
We present infrared spectra for gas phase vanadium oxide cluster anions. Structures are
assigned on the basis of comparison between measured spectra and DFT calculations. We
- -
concentrate on the cluster size between V2O6 and V8O20 . Cage structures, which were originally
predicted, [1] have now been spectroscopically identified for the first time. The spectra show
three characteristic absorption regions of the IR spectrum which correspond to three different
vibrational modes, namely the peroxo-modes at highest energies around 1100 cm -1 , the vanadylmodes
in the intermediate region from 920 to 1020 cm -1 , and the V-O-V modes below 900 and
to about 600 cm -1 . The smallest clusters studied, the divanadium oxide anions, can be classified
-
as “quasi-planar”, characterized by nearly planar V-O-V-O ring. V3O8 is an intermediate case; it
-
is the first anion that shows a three dimensional backbone structure. V4O10 is the first cage
structure, in which each vanadium atom forms three V-O-V bonds and one vanadyl bond. Cages
-
are observed for all larger clusters up to V8O20 , indicating that these are particular stable
-
structures. The spectrum of V4O20 (see figure) reveals some striking similarities with the
properties of a vanadium oxide single crystal surface[2] suggesting it is an interesting candidate
for studying surface adsorption and surface reactivity on a model system in the gas phase.
References
Fragment Ion Signal
Intensity
0
0
Photon Energy (cm -1 )
600 700 800 900 1000 1100 1200 1300 1400
V-O(3)
O-V-O
V-O(2)
V=O
V-O(1)
IR-PD (gas phase)
V 8 O 20 ¯→ V 4 O 10 ¯ + V 4 O 10
HREELS (surface)
600 700 800 900 1000 1100 1200 1300 1400
Electron Energy Loss (cm -1 )
[1] S. F. Vyboishchikov and J. Sauer, J. Chem. Phys. A 105, 8588 (2000).
[2] B. Tepper, B. Richter, A.-C. Dupuis, H. Kuhlenbeck, C. Hucho, P. Schilbe, M. A. bin Yarmo, and
H.-J. Freund, Surface Science 496, 64 (2002).
59

B - 22
60
Probing the Electronic Structure and Chemical Bonding of Metal
Oxide Clusters Using Photoelectron Spectroscopy
Hua-Jin Zhai, B. Kiran, Xi Li, and Lai-Sheng Wang
Department of Physics, Washington State University, 2710 University Drive, Richland, WA 99352, USA
and W. R. Wiley Environmental Molecular Sciences Laboratory and Chemical Science Division, Pacific
Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA
We report investigations of the electronic structure and chemical bonding of metal oxide
clusters using photoelectron spectroscopy and theoretical calculations. One key advantage of
cluster studies is the flexibility to create clusters with any stoichiometry. It was shown [1] that
metal oxide clusters with fixed numbers of metal atoms exhibit a behavior of sequential
oxidation up to the maximum oxidation state of the metal atoms. For oxygen-rich clusters, O2
unit begins to appear as per- or super-oxide. In this work, we show our recent investigation of
Mo and W oxide clusters (MoOx - and WOx - , x = 3-5) [2]. Comparisons between photoelectron
spectra and theoretical calculations are used to provide detailed information about the structures
and chemical bonding of the oxide clusters. The MO3 molecules are stoichiometric species and
are observed to be closed shell with large energy gaps. However, we observe that the O2 moiety
does not appear in the O-rich MO4 species, which exhibit a distorted tetrahedral structure with
diradical character because of the strong M-O bonding. WO5 is found to be an unusual chargetransfer
complex, (O2 - )WO3 + , also with diradical character.
We will also report recent studies on the electronic structure of polyoxometalate anions (PMAs)
using electrospray and photoelectron spectroscopy [3]. PMAs are a class of well-defined and
negatively charged nanoclusters that exist in solution. The electrospray technique allows these
species to be studied in the gas phase, facilitating direct comparisons between theory and
experiment.
References
[1] L. S. Wang, H. Wu, and S. R. Desai, Phys. Rev. Lett. 76, 4853-4856 (1996).
[2] H. J. Zhai, B. Kiran, L. F. Cui, X Li, D. A. Dixon, and L. S. Wang, J. Am. Chem. Soc. 126, 16134-
16141 (2004).
[3] X. Yang, T. Waters, X. B. Wang, R. A. J. O’Hair, A. G. Wedd, D. A. Dixon, J. Li, and L. S. Wang,
J. Phys. Chem. A 108, 10089-10093 (2004).

Interaction of oxygen with mass-selected Ag cluster anions and
nanoparticles
Ignacio Lopez-Salido, Dong Chan Lim, Gerd Ganteför, and Young Dok Kim
Department of Physics, University of Konstanz, D-78457 Konstanz, Germany
http://www.clusterphysik.uni-konstanz.de/
B - 23
Adsorption of oxygen on free negatively charged Ag clusters were studied using Time-of-
Flight mass spectrometry and photoelectron spectroscopy. In contrast to the results of Au cluster
anions, which become inert towards oxygen chemisorption for Au n - with n > 20, Ag clusters
consisting of more than 30 atoms are still reactive towards O 2 chemisorption. The even-odd
alteration of the O 2 chemisorption reactivity was found, which has been also observed for the
Au cluster anions. Photoelectron spectroscopy was used to study the nature of oxygen species
on the Ag cluster anions. To shed light on the chemical properties of larger Ag nanoparticles,
we deposited Ag on Highly Ordered Pyrolytic Graphite (HOPG) surfaces, leading to the
formation of Ag nanoparticles with particle diameters up to 10 nm. Scanning Tunneling
Microscopy (STM) and X-ray Photoelectron Spectroscopy (XPS) results suggest quite narrow
size distributions of Ag islands on HOPG, allowing investigations on size dependent changes of
electronic and chemical properties of Ag nanoparticles. For the Ag nanoparticles smaller than
10 nm, completely different oxidation patterns were observed compared to the Ag bulk crystal.
We found Ag oxide species, which cannot be observed by oxidation of Ag bulk crystal.
Implication of this result in heterogeneous catalysis is discussed in connection with the size
selectivity in ethylene epoxidation.
61

B - 24
62
Joint theoretical and experimental investigations of reactivity of
anionic and cationic gold oxide clusters with carbon monoxide
Christian Bürgel 1 , Roland Mitrić 1 , Vlasta Bonačić-Koutecký 1 , Michele L. Kimble 2 , Nelly A. Moore 2 , A.
Welford Castleman Jr. 2
1 Humboldt Universität zu Berlin, Institut für Chemie, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany
2 Department of Chemistry and Physics, Pennsylvania State University, University Park, Pennsylvania
16802, USA
Recent literature shows that gold oxides, containing both atomic and molecular oxygen may
play a role as the active site in supported gold catalysts. Therefore, a fundamental question can
be raised as to whether it is sufficient to have an atomic oxygen in order for the oxidation
reaction to proceed. A second fundamental question concerns the role of a charge. We will
address both aspects by presenting the oxidation of CO in the presence of anionic and cationic
gas phase gold oxide clusters. The influence of the charge on the association and replacement
reaction has been also investigated. The experimental studies were carried out utilizing a metal
ion flow tube in conjunction with a guided ion beam apparatus where gold oxides with both
atomized and molecular oxygen are produced. Based on DFT and CCSD calculations we
identified the reactive center and proposed reaction mechanisms. It will be shown that a
peripheral O-atom is the most effective center for the oxidation reaction, while cooperative
effects are mandatory for a reaction to proceed if molecular oxygen is involved. However, the
presence of atomic oxygen does not guarantee that the oxidation reaction will proceed. We also
wish to show the importance of cationic clusters for the association and replacement reactions.
References
[1] M. L. Kimble, A. W. Castleman, Jr., R. Mitrić, C. Bürgel, V. Bonačić-Koutecký, J. Am. Chem.
Soc., 126, 2526 (2004).
[2] M. L. Kimble, C. Bürgel, Nelly A. Moore A. W. Castleman, Jr., R. Mitrić,
V. Bonačić-Koutecký, J. Am. Chem. Soc., in prep.

Dynamics
63

Photoionization Dynamics of Pure Helium Droplets
Darcy S. Peterka 1,2 , Jeong Hyun Kim 2 , Chia Wang 1 , Musahid Ahmed 2 , Daniel M. Neumark 1,2
B - 25
1 College of Chemistry, University of California, Berkeley, Address, Berkeley, 94720, USA
2 Chemical Sciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley, Ca
94720, USA
Helium nanodroplets have been demonstrated to provide a unique environment for
spectroscopic studies. Their ability to capture and cool foreign dopants in a controlled way has
led to their description as an "ultracold nanolaboratory". Many groups have used this property to
their advantage, performing rotational and vibrational spectroscopic studies in great detail, with
slightly less work being done by probing electronic transitions. However, there is almost no
work on the photoionization of pure clusters. We have studied the single photon vacuum
ultraviolet ionization of pure helium droplets below the atomic helium ionization threshold
using velocity-mapped photoelectron imaging. We see wavelength dependant changes in the
ionization dynamics of the droplet. Below the atomic threshold, indirect processes are the
dominant source of electrons, leading to electrons of very low kinetic energy 1 . With photon
energies larger than the Helium atom ionization energy, direct ionization to Hen + takes place,
giving fast photoelectrons.
References
[1] D. S. Peterka, A. Lindinger, L. Poisson, M. Ahmed, and D.M. Neumark, Phys. Rev. Lett. 91,
043401 (2003).
65

B - 26
66
Excited-state relaxation dynamics in Au cluster anions
J. Stanzel, F. Burmeister, M. Neeb, W. Eberhardt
BESSY GmbH, Albert-Einstein-Str. 15, 12489 Berlin
We report on time-resolved two-photon photoemission measurements on small gold cluster
anions (Aun - , n = 6, 7, 8, 9, 14, 20). These measurements were performed to monitor the
relaxation dynamics of optically excited states. As reported recently optically excited electronic
states in Au3 - and Au6 - are long lived (> 1 ns) [1] in comparison to open d-shell metal clusters as
Pt, Pd, Ni [2] and W [3]. This is mainly attributed to the large HOMO-LUMO band gap of gold
clusters, which minimizes the probability of fast electron-electron-scattering. As we will present
here, larger Au-clusters, e.g. Au8 - (fig. 1) can show relaxation processes in the lower picosecond
range.
Figure 1. Time resolved two-photon photoemission spectra of Au 8 - : The peak at 2.9 eV binding energy is recorded
with the probe pulse (3.12 eV) and is assigned to the HOMO. In the pump & probe spectra (pump: 1.56 eV) a peak
appears above the HOMO at 1.4 eV with its maximum at a delay of 0.1 ps. At longer delay times this peak broadens
and shifts to higher binding energies until it completely vanishes.
References
[1] M. Niemietz, P. Gerhardt, G. Ganteför, Y.D. Kim, Chem. Phys Lett., 380, 99 (2003).
[2] N. Pontius, M. Neeb, W. Eberhardt, G. Lüttgens, P. S. Bechthold, Phys. Rev. B 67, 354251 (2003)
and references therein.
[3] to be published.

Fast Electronic Relaxation in Metal Clusters via Excitation of
Coherent Shape Deformations: Slipping Through a Bottleneck
V. V. Kresin 1 , Yu. N. Ovchinnikov 2 , V. Z. Kresin 3
1 Dept. of Physics, University of Southern California, Los Angeles, California 90089-0484, USA
2 Landau Institute for Theoretical Physics, Russian Academy of Sciences, Moscow 117332, Russia
3 Lawrence Berkeley Laboratory, University of California, Berkeley, California 94720, USA
B - 27
We introduce and analyze a channel of electronic relaxation in metallic clusters which
enables large energy transfer to the ionic subsystem and, correspondingly, fast electron
relaxation dynamics. The discreteness of electronic levels in finite size-quantized systems such
as metal nanoparticles, quantum dots, etc., represents a challenge for understanding the
relaxation behavior of excited electrons. As is known, cases when the spacing between
electronic energy levels exceeds the vibrational frequencies raise the prospect of so-called
relaxation bottleneck phenomena. That is to say, if in order to drop to a lower-lying level an
excited electron needs to emit multiple simultaneous vibrational quanta, the probability of such
a transition should be strongly suppressed: multiphonon processes normally occur only as high
order interaction corrections.
The proposed relaxation mechanism which overcomes the bottleneck involves the special ability
of free clusters to deform. A cluster with an electron in a previously unoccupied orbital (e.g.,
excited by light or externally injected) will proceed to deform from its original shape.
Microscopically, this deformation invalidates the selection rule which in the lowest order allows
only single-phonon processes: whereas the rule assumes that the ionic equilibrium position is
fixed during the electronic transition, a shift in the cluster’s ionic framework can produce a
coherent multiphonon transition without any additional smallness. We have developed a method
which allows us to describe the evolution of the deformation parameter up to the level crossing
point, followed by electronic intershell transitions. The process is analogous to internal
conversion in polyatomic molecules, but generally involves more than a single pair of electronic
orbitals. It is found that the corresponding relaxation time indeed can be quite short.
As an application, we have performed a model calculation for aluminum clusters. This was
motivated by recent experimental work [1] which used time-resolved two-photon photoemission
of Aln¯ (n=6-15) to demonstrate that the intermediate electronic state decays within a few
hundred femtoseconds in all of the above cluster sizes, even in the closed-shell Al13¯. Our
results are in agreement with the observed lifetime.
This work was supported by the NSF (V.V.K.), a NATO Collaborative Linkage Grant (V.V.K.
and Yu.N.O.), and DARPA (V.Z.K.).
References
[1] P. Gerhardt, M. Niemietz, Y. D. Kim, G. Ganteför, Chem. Phys. Lett. 382, 454 (2003).
67

B - 28
68
Femtosecond Laser-Induced Fusion of Fullerenes Inside Clusters
Martin Hedén, Klavs Hansen, Eleanor E. B. Campbell
Department of Physics, Göteborg University, SE-41296 Göteborg, Sweden
The interaction of fullerene molecules with femtosecond laser radiation has been the subject
of much interest in recent years. One interesting observation is the clear separation of different
ionisation mechanisms that can be observed as a function of the timescale for the excitation [1].
We have shown that for intermediate timescales (ca. 70-300 fs) the ionisation can be largely
regarded as a thermal electron emission from the equilibrated hot electron system before energy
is transferred to the nuclear degrees of freedom [2]. Interesting dynamics have also been
observed in collisions between fullerenes leading to molecular fusion of the collision partners
and the formation of a metastable larger fullerene that subsequently decays by the emission of
C2 molecules [3].
In this contribution we combine these two topics of recent research interest and show that it is
possible to induce molecular fusion of fullerenes that are weakly (van der Waals) bonded in
molecular clusters. Fig. 1. Shows a typical mass spectrum of the clusters after laser irradiation.
The fragmentation pattern is clearly reminiscent of C2 emission from a large fullerene-like
structure. We show that this observation is consistent with our knowledge of both the ionisation
mechanisms of C60 on irradiation with fs laser pulses and with our knowledge of the energetic
threshold for fullerene fusion and the C2 decay of large fullerenes. It is shown that substantial
atomic rearrangement can take place on a timescale shorter than that needed for the complete
destruction of the highly excited cluster. This is different for the observations made in
experiments where fullerene clusters are collided with highly charged ions [4]. Reasons for the
difference will be discussed.
N
Figure 1. Time-of-flight mass spectrum from fullerene clusters after excitation with a 200 fs laser pulse.A distribution
of fragment masses is seen corresponding to each cluster size, with a mass separation of the fragments in each
distribution of C2. This is a clear indication that the clusters have ionised and then had time for extensive atomic
rearrangement to form a single large fullerene-like structure before the original clusters completely disintegrate.
References
counts
10000
1000
60 80 100 120 140 160 180 200 220 240 260 280 300
[1] E.E.B. Campbell, K. Hansen, K. Hoffmann, G. Korn, M. Tchaplyguine, M. Wittmann, I.V. Hertel,
Phys. Rev. Lett., 84 2128 (2000)
[2] K. Hansen, K. Hoffmann, E.E.B. Campbell, J. Chem. Phys. 119 2513 (2003).
[3] E.E.B. Campbell, A.V. Glotov, A. Lassesson, R.D. Levine, C.R. Physique 3 (2002) 341
[4] B. Manil, L. Maunoury, B. A. Huber, J. Jensen, H. T. Schmidt, H. Zettergren, H. Cederquist, S.
Tomita and P. Hvelplund, Phys. Rev. Lett. 21 (2003) 215504

Femtosecond photoelectron spectroscopy of sodium clusters
Abdollah Malakzadeh, Christian Hock, Christof Bartels, Raphael Kuhnen and Bernd v. Issendorff
Fakultät für Physik, Universität Freiburg, H.Herderstr. 3, 79104 Freiburg, Germany
B - 29
Recently we have shown that the electron gas in a free sodium cluster can be heated by a
single fs-laser pulse to temperatures high enough for thermal electron emission to occur [1,2].
This emission can be described by a simple model: the laser excites the collective motion of the
electrons (the plasmon), which after a very short time (a few fs) decays into single electron-hole
excitations. Due to the strong electron-electron interaction within a short time this nonthermal
energy distribution of the electrons is transformed into a thermal one. The electron gas then
cools by electron-phonon coupling.
Time-resolved pump-probe photoelectron and photofragmentation spectroscopy has been
applied to measure the electron-phonon-coupling constant as a function of cluster size. This has
been done using relatively long laser pulses (τ ≈ 200 fs). In order to obtain more information
about the early stages of the excitation, shorter laser pulses are necessary. Therefore a NOPA
(noncolinear optical parametric amplifier) has been constructed, which allows the production of
wavelength tunable, short (τ < 50 fs) laser pulses, as well as a hollow capillary compressor.
The performance of these devices and first results for sodium clusters are discussed.
References
[1] R.Schlipper, R. Kusche, B.v.Issendorff and H.Haberland, App. Phys. A. 72, 255 (2001)
[2] M.Maier, M. Astruc Hoffmann, and B.v. Issendorff, NJP 5, 3 (2003)
69

B - 30
70
Photoelectron Spectroscopy on Small, Size Selected, Neutral Silver
Clusters Embedded in Helium Droplets
Andreas Przystawik, Paul Radcliffe, Josef Tiggesbäumker, Karl-Heinz Meiwes-Broer
Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock, Germany
Experiments on neutral clusters are often hampered by a broad distribution of cluster sizes.
Therefore most of the work concerning the electronic structure of clusters is performed with
charged particles, where one can prepare a molecular beam of species with a certain number of
atoms. We present a possibility to exploit absorption resonances to select a cluster size for
excitation and ionization from the neutral beam.
This technique is used to record two-photon photoelectron spectra of small silver clusters grown
in helium nanodroplets by the pickup method. We derive information on both, the cluster and its
electronic structure, and the interaction with the helium environment. An analysis of the spectra
recorded at different wavelengths shows that all investigated systems undergo a rapid relaxation
on a picosecond timescale to the lower edge of the broad excitation, see figure 1.
One possibility of helium pickup sources is to prepare clusters in high spin states as already
demonstrated with alkali clusters on the surface of droplets [1]. Despite the lack of selectivity in
favor of high spin states when growing the clusters inside the droplet we can clearly detect
silver dimers in triplet states not present in gas phase spectroscopy.
Figure 1. Schematic diagram of the ionization dynamics of Ag 8 [2]. After excitation to the unoccupied band E *
roughly 4.0 eV above the ground state, the cluster quickly relaxes to the lower edge EL. In a R2PI
experiment, ionization occurs from this long-living level.
References
[1] P. Claas, D. Schumacher, and F. Stienkemeier, Phys. Rev. Lett. 92, 013401 (2004).
[2] P. Radcliffe et al., Phys. Rev. Lett. 92, 173403 (2004).

Signatures of the Giant Dipole Resonance in the Response of Metal
Clusters for Strong-Field Dual-Pulse Excitation
Thomas Fennel, Tilo Döppner, Josef Tiggesbäumker and Karl-Heinz Meiwes-Broer
Institut für Physik, Universität Rostock, Universitätsplatz 3, 18051 Rostock , Germany
B - 31
The response of metal clusters irradiated with a sequence of two femtosecond laser pulses is
strongly dependent on the optical delay between the pulses. Recent experiments have shown
that the adjustment of the delay provides a powerful way to control the coupling of strong laser
radiation to finite systems. Both the yield of highly charged ions [1] as well as the kinetic
energy of emitted electrons is strongly enhanced for a particular optimal delay. The dynamics of
the signals is much more pronounced compared to earlier measurements using stretched
pulses [2].
For the investigation of the time-dependent interaction of dual pulses with simple metal clusters
numerical simulations have been performed using Thomas-Fermi-Vlasov molecular dynamics
(TFV-MD) [3]. The semiclassical treatment allows a fully three-dimensional microscopic
simulation of the laser-cluster interaction and provides a reasonable description of delocalized
electrons in the cluster groundstate as well as the violent nonlinear response to a strong field
close to TDLDA.
Simulations on Na55 and Ag55 show that also in the strong field regime the most effective
absorption is caused by resonant excitation of multi-plasmon modes. The calculations are in
qualitative agreement with the measurements and clearly reproduce an optimal optical delay for
enhanced ionization of the cluster [1], see Fig. 1, as well as a strong energy enhancement in the
electron emission.
Figure 1. (a) Calculated average charge of emitted ions after dual-pulse excitation of Na55 as a function of
the optical delay. Both pulses have a width of 50fs at a wavelength of 800nm. (b) Measured normalized
dual-pulse signals of Ag 5+ from the explosion of silver clusters in helium droplets, resulting from the
excitation with 130 fs pulses. Taken from Ref. [1].
References
[1] Döppner, Fennel et al., Phys. Rev. Lett, in press
[2] Köller, Schumacher, Köhn et al., Phys. Rev. Lett. 82:3783, 1999
[3] Fennel, Bertsch and Meiwes-Broer et al., Eur. Phys. J. D 29:367, 2004
71

B - 32
Fragmentation of small alkali cluster attached to helium nanodroplets
72
Patrick Claas 1 , Georg Droppelmann 1 , Claus-Peter Schulz 2 and Frank Stienkemeier 1
1 Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, D-33615 Bielefeld, Germany
email: franks@physik.uni-bielefeld.de
2 Max-Born-Institut, Max-Born-Str. 2a, D-12489 Berlin, Germany
We use helium nanodroplet isolation (HENDI) to form cold small alkali clusters. In
particular, potassium atoms are picked up successively by superfluid helium droplets in order to
aggregate to clusters at temperatures of 380 mK. In a femtosecond pump-probe setup we
determine fragmentation times of the clusters upon electronic excitation. In contrast to earlier
experiments on free clusters (cf. Figure 1) we find substantially longer times in the
fragmentation processes. The following aspects have to be considered: (a) population of highspin
states [3]; (b) missing thermal activation because of the low temperature; (c) cage effects
by the helium environment. Studies performed at different photon energies, droplet sizes, etc.
allow a closer look at the fragmentation mechanism and the items given above.
Furthermore first results are presented on the formation of complexes of alkali clusters with
foreign atoms or molecules (e.g. H2O) attached to helium droplets.
decay time [ps]
Figure 1.: Fragmentation times upon femtosecond laser excitation of potassium clusters K n attached to helium
nanodroplets as a function of cluster size. As a comparison results of gas-phase clusters by Wöste et al. are also
included.
References
10
1
2 4 6 8 10
cluster size n
[1] H. Kühling et al., J. Phys. Chem. 98, 6679 (1994).
[2] A. Ruff et al., Z. Phys. D 37, 175 (1996).
[3] C. P. Schulz, et al., Phys. Rev. Lett. 92(1), 013401 (2004) .
this work, 1.55eV, K
this work, 1.47eV, K
[1], 1.47 eV, K
[1], 2.94 eV, K
[2], 2.92 eV Na

Embedding of Na clusters in raregas matrices
F. Fehrer 1 , P.-G. Reinhard 1 , E. Suraud 2 , M. Dinh 2 , G. Bousquet 2
1 Institut für theoretische Physik, Universität Erlangen, Staudtstrasse 7, D-91058 Erlangen, Germany
2 Laboratoire de Physique Quantique, Universite Paul Sabatier, 118 Route de Narbonne,
F-31062 Toulouse, cedex, France
B - 33
We have developed a microscopic model for the description of a Na-cluster embedded in a
raregas (Rg) substrate. The cluster valence electrons are treated at the level of TDLDA. The Rgatoms
are considered as classical point-particles interacting with the cluster-electrons via local
pseudopotentials. In order to describe the polarization of the raregas, we ascribe each Rg-atom a
time-dependent dipolemoment. A short range repulsive Rg-core-potential together with a term
taking the vdW-interaction into account is added. The model is calibrated to reproduce bindingproperties
of the NaRg molecule and bulk Rg.
We first study the influence of the Rg on the optical response of the cluster. We then investigate
the coupled nonlinear dynamics of cluster and matrix following a strong laser excitation.
73

B - 34
Relaxation Dynamics of Optically Excited States of Ag Cluster Anions
74
Markus Engelke, Marco Niemietz, Young Dok Kim, Gerd Ganteför
Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany
http://www.clusterphysik.uni-konstanz.de/
For bulk metals, optically excited electronic states can relax within few tens of
femtoseconds due to very fast Auger-like electron-electron scattering processes. As the size of a
particle decreases, changes in relaxation dynamics of optically excited states are observed [1,2].
Using Time-Resolved Two-Photon Photoemission (TR-PPE) spectroscopy, relaxation times of
optically excited states of Ag cluster anions consisting of less than 22 atoms (pump photon
energy of 1.5 eV) were determined. For Ag18 - , Ag19 - and Ag21 - , relaxation times amount to about
500 femtoseconds, which are significantly longer than those of d-metal clusters consisting of
less than 8 atoms [3]. The long life times of the excited states of these Ag cluster anions can be
explained by lower density of states above the upper levels of the non-excited electrons within
the pump photon energy in these clusters, caused by a large gap between 2s and 1f electronic
shells, i.e. electronic shell configurations significantly affect the electron relaxation dynamics.
-
Ag18 Intensity (a.u.)
References
0 fs
133 fs
266 fs
932 fs
1,9 ps
12,9 ps
48,6 ps
0 1 2
Binding Energy (eV)
Figure 1. TR-PPE spectra of Ag 18 - . A distinct peak can
be observed at a binding energy of about 1.3 eV,
accompanying broad states at higher binding energies.
The state at 1.3 eV can be attributed to the excitation of
an electron in the HOMO to an unoccupied state. As the
delay between pump and probe photons increases, the
signals between 1.2eV - 2.5 eV attenuate. By assuming
an exponential decay of the excited state, the lifetime is
estimated to be about 420 fs.
[1] J.R.R. Verlet, A.E. Bragg, A. Kammrath, O. Cheshnovsky, and D.M. Neumark,
J. Chem. Phys. 121, 10015 (2004).
[2] M. Niemietz, P. Gerhardt, G. Ganteför and Y. D. Kim, Chem. Phys. Lett. 380, 99 (2003).
[3] N. Pontius, M. Neeb, W. Eberhardt, G. Lüttgens, P. S. Bechthold, Phys. Rev. B 67, 354251 (2003)
and references therein

Theoretical studies of ultrafast processes in clusters and metalbiomolecule
complexes
Roland Mitrić, Vlasta Bonačić-Koutecký
B - 35
Humboldt Universität zu Berlin, Institut für Chemie, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany
Our theoretical approach for exploration of ultrafast dynamics is based on combination of
the adiabatic and nonadiabatic ab initio MD ’on the fly’ with the Wigner distribution approach
and permits to include all degrees of freedom. We show that it allows to accurately simulate
femtosecond spectra in complex systems involving both ground and excited electronic states
and to reveal the underlying dynamical processes [1].
This will be illustrated on the following examples:
i) Real time investigation of the ultrafast processes in the ground and excited states of noble
metal clusters can provide insights relevant for understanding of their reaction dynamics. We
present the simulation of the fs signals of the Ag2Au − /Ag2Au/Ag2Au + [2] system in the
framework of the NeNePo spectroscopy. This allowed us to establish conditions under which
the geometric relaxation can be distinguished from the IVR process which plays a crucial role
for the stabilization of the complexes between the cluster and reacting molecule (e. g. O2 or
CO). Study of cluster size effects on the dynamics in the excited electronic states of anionic
clusters have been explored on the example of the Au5 − and Au7 − with the perspective to
identify the dynamical processes in the time resolved photoelectron spectra. Based on these
studies we propose the resonant two photon NeNePo technique, involving anionic excited
states, which may serve for control of the reactivity of clusters.
ii) Interplay between nonradiative and radiative relaxation processes play an important role in
the design of efficient light-emitting materials. Influence of nonadiabaticity on the ultrafast
excited state dynamics in the third 1 1 B1 electronic state of Na3F cluster has been investigated
employing the ab initio MD ’on the fly’ in the framework of TDDFT [1,3] and CI methods. The
simulated pump-probe signals exhibit characteristic oscillations at early times which are in good
agreement with experimental results [3]. At later times simulations of the nonadiabatic
dynamics in the framework of the CI method allow us to estimate the nonradiative lifetime.
iii) Formation of complexes between silver clusters and tryptophan can possibly lead to
enhancement of the light absorption and to fluorescence. Therefore, the influence of Ag + cation
on the conformation and optical properties of tryptophan has been investigated. For this purpose
we employ the combination between semi-empirical CI methods with the MD ”on the fly”.
These studies serve as a starting point for the exploration of emissive properties and ultrafast
dynamics.
References
[4] V. Bonačić-Koutecký, R. Mitrić, Chem. Rev., 105, 11 (2005).
[5] T. M. Bernhardt, J. Hagen, L. D. Socaciu, J. Le Roux, D. Popolan, M. Vaida, L.Wöste, R.
Mitrić, V. Bonačić-Koutecký , A. Heidenreich, J. Jortner, ChemPhysChem, 6, 243 (2005).
[6] M. C. Heitz, G. Durand, F. Spiegelman, C. Meier, R. Mitrić, V. Bonačić-Koutecký, J. Chem.
Phys., 121, 9906 (2004).
75

B - 36
76
Rapid Alloying in binary Clusters: A Molecular Dynamics Study
Y. Shimizu, T. Kobayashi, K. S. Ikeda and S. Sawada
Ritsumeikan University, Kwansei Gakuin University
Dynamics of surface atoms penetrating into microclusters is investigated in connection with
the very rapid alloying (RA) in metal microclusters. RA was experimentally discovered by
Yasuda and Mori for various types of nano-sized binary metal clusters. In short, RA is a
manifestation of an unexpectedly fast diffusion of solute atoms into a host cluster, which is
controlled by the magnitude of heat of solution and size of a cluster. Isothermal molecular
dynamics simulation is done to investigate the mechanism of RA.
In particular, we put our focus upon a cooperative interplay between atomic rearrangement
along a cluster surface and that along radial direction of a cluster.
Our results are summarized in the following two points. The dependence of the alloying and
that of radial diffusion upon negative heat of solution are elucidated. It is found that dependency
of the “alloying rate” upon the negative heat of solution and the size of clusters reproduced the
qualitative features observed in the experiments. To quantify the dependence of atomic
rearrangement dynamics upon temperature, the activation process of diffusive motion of atoms
is analyzed.
Although the activation energy of radial diffusion is about two times as large as that of
surface diffusion, there are circumstantial evidences that the latter process controls the former
one. In that sense the rapid radial diffusion of a surface atom into a cluster is caused by the
surface diffusion unlike the usual diffusion in bulk solid. In order to clarify the mechanism
converting the active surface motion into the rapid radial diffusion, we numerically enumerate
reaction paths. We found some candidates of characteristic collective motion which would
effectively induce the rapid radial diffusion in terms of the surface activity.
These two results suggest that surface atoms diffuse into the inside of the cluster due to the
accumulation of active surface motion during long-time dynamics beyond a microsecond, even
though the cluster is almost in solid-phase. Whilst diffusion due to the mechanism is crucial for
the onset of RA, the same atomistic process is similarly expected not only for binary clusters,
but also for monotonous ones. It leads us to an idea that a microcluster can be viewed as a
dynamic material in which a transport of atoms between the surface area and the core region is
continually induced in the course of long time scale.

Magnetism
77

Electronic and Magnetic Properties of
Lanthanide Organometallic Clusters
Atsushi Nakajima
Department of Chemistry, Faculty of Science and Technology, Keio University & JST-CREST,
3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
B - 37
Binary systems are very important to create functionality of materials, and binary clusters
consisting of a few to hundreds atoms provide microscopic viewpoints toward chemical
bonding, geometry, and electronic structures including spin states. For metal and organic
ligands, a variety of 1D, 2D, and 3D structures are formed depending on their combinations, and
they exhibit novel electronic properties, such as electron delocalization and multiple charge
transfers.
With the aid of proper organic ligands, 1D structures are preferably formed in gas phase
reaction. For example, Eum(C8H8)n sandwich clusters were produced in gas phase by mixing the
vapor of europium (Eu) atoms and 1, 3, 5, 7-cyclooctatetraene (C8H8) molecules and 18-layered
clusters were produced at maximum, which is about 8 nm length. With photoionization and
photoelectron spectroscopies, formation mechanism and electronic structures will be presented
in the viewpoint of sequential reactions with harpoon mechanism.
In the design of molecular magnetic materials, furthermore, a subject to conquer is how to
align the spin in the cluster. One-dimensional sandwich clusters are an interesting target since
their magnetism should reflects geometric anisotropy and the condition of electronic spins on
each layer. Stern-Gerlach type magnetic deflection measurements were performed for two types
of multiple sandwich clusters: vanadium-benzene Vn(C6H6)n+1 and terbium-cyclooctatetraene
Tbn(C8H8)n+1. Beams of Vn(C6H6)n+1 clusters (n = 1-4) showed symmetric broadening induced
by the inhomogeneous field, indicating free spin behavior similar to that displayed by isolated
paramagnetic atoms. By contrast, beams of Tbn(C8H8)n+1 clusters displayed one-sided deflection,
indicating that fast spin relaxation occurs within the clusters. The difference in the magnetic
deflection behavior exhibited by these two systems is explained by their electronic structures,
specifically the bonding characteristics between metal atoms and ligand molecules.
References
[1] A. Nakajima, K. Kaya “A novel network structure of organometallic clusters”
JPC A 104, 176 (2000).
[2] S. Nagao, A. Nakajima, K. Kaya “Multiple-decker sandwich poly-ferrocene clusters”
JACS 122, 4221 (2000).
[3] K. Judai, K. Yagi, S. Yabushita, A. Nakajima, K. Kaya “A soft-landing experiment of organometallic
cluster ions: infrared spectroscopy of V(benzene)2 in Ar matrix” CPL 334, 277 (2001).
[4] K. Miyajima, T. Yasuike, S. Yabushita, A. Nakajima, K. Kaya “The quasi-band electronic structure
of Vn(Benzene)n+1 clusters” JPC A 106, 10777 (2002).
[5] K. Miyajima, A. Nakajima, S. Yabushita, M. B. Knickelbein, and K. Kaya “Ferromagnetism in onedimensional
vanadium-benzene sandwich clusters” JACS 126, 13202 (2004).
[6] N. Hosoya, R. Takegami, K. Miyajima, M. B. Knickelbein, S. Yabushita, A. Nakajima “Lanthanide
organometallic sandwich nanowires: formation mechanism” JPC A (Letter) in press.
[7] K. Miyajima, M. B. Knickelbein, A. Nakajima “Stern-Gerlach studies of organometallic sandwich
lusters” EPJD in press.
79

B - 38
80
Mn clusters: a nanoscale magnetic transition
Sudha Srinivas and Koblar Alan Jackson
Department of Physics, Central Michigan University, Mount Pleasant, Michigan 48859, USA
Small Mn clusters exhibit remarkable magnetic behavior. Early ESR experiments[1] found
the smallest clusters (n=2-5) to be ferromagnetic (FM), with total net spin corresponding to 5 µB
per atom, the Hund’s rule value for an isolated Mn atom. Later Stern-Gerlach measurements[2]
found larger clusters (n>12) to have very small net moments. For example, Mn13 was found to
have a net moment of only 3 µB for the entire cluster. Our recent calculations[3,4] explain that
these data reflect a transition in magnetic ordering as a function of cluster size, occurring at n=7
atoms. Specifically, the FM arrangements of the atomic spins favored in smaller clusters give
way to antiferromagnetic (AF) arrangements in larger clusters. The calculations indicate that the
FM → AF transition occurs at n=7, in agreement with experimental data, and is driven by a
large change in the relative energies of the FM and AF structures. For n

The magnetic moments of isolated metal clusters
Gereon Niedner-Schatteburg 1 and Wilfried Wurth 2
1 Fachbereich Chemie, TU Kaiserslautern, Germany (gns@chemie.uni-kl.de)
2 Institut für Experimentalphysik, Universität Hamburg, Germany (wilfried.wurth@desy.de)
B - 39
Within the last fiveteen years X-ray Magnetic Circular Dichroism (XMCD) has made itself
useful in solid state physics and in surface science [2] since it allows for the elucidation of
magnetic properties that would be unavailable otherwise. For chemists XMCD has become a
valuable tool when investigating paramagnetic organometalic and coordination compounds [2].
In a few cases even paramagnetic metalloproteins have been studied successfully [3]. Only
recently size selected iron clusters became subject of XMCD measurements [4]. All of these
studies, however, have utilized condensed phase samples. Substrates and solvents may exert
decisive but unknown influence on the magnetic properties of deposited and desolved samples,
respectively. It is mandatory to identify suitable model systems for direct investigation and void
of such an interference.
We propose to apply XMCD to isolated gas phase metal clusters of selected sizes. This novel
experimental scheme shall allow for determination of total magnetic moments as arising
through spin and orbit contributions. Temperature tuning shall enable the recording of
magnetization curves.
This shall be enabled through application of circularly polarized x-ray synchrotron radiation
(600eV) to isolated gas phase transition metal clusters which have been size selected and stored
in an ion trap [5,6] under high vacuum.
The talk shall outline the basic features of the proposed scheme and it is going to suggest a
particular way to carry out actual experiments.
References
[1] G. Schütz et al., Phys. Rev. Lett. 58, 737 (1987); C. T. Chen, N.V. Smith, and F. Sette, Phys. Rev.
B 43, 6785 (1991); B. T. Thole et al., Phys. Rev. Lett. 68, 1943 (1992); M. Altarelli, Phys. Rev. B
47, 597 (1993); C. T. Chen et al., Phys. Rev. B 48, 642 (1993); Y. U. Idzerda et al., Surf. Science
287/288, 741 (1993)
[2] S. P. Cramer in: ACS Symposium series Vol. 858 (2003)
[3] J. Van Elp. et al., Proc. Nat. Acad. Sci. U.S.A. 90, 9664 (1993)
[4] S. T. Lau, A. Föhlisch, R. Nietubyc, M. Reif, and W. Wurth, Phys. Rev. Lett. 89, 057201 (2002)
[5] G. Niedner-Schatteburg and V. E. Bondybey, Chem. Rev. 100, 4059 (2000)
[6] A. Lagutschenkov et al., Poster, S 3 C, Brand 2005
81

Materials
83

B - 39
84

Intensity
10000
8000
6000
4000
2000
Stable Clusters of Layered Semiconductors Prepared by Laser
Ablation
M. Galak 1 , O. Yeschenko 1 , I. Dmitruk 1 , V. Romanyuk 2 , A. Kasuya 2
540
500 600 700 800 900
wavelength, nm
B - 40
1 Department of Physics, National Taras Shevchenko Universityof Kyiv, prosp. akad. Glushkov 2, Kyiv,
01022, Ukraine
2 Center for Interdisciplinary Research, Tohoku University, Sendai, 980-8578, Japan
The aim of the research presented is to investigate cluster formation under pulsed laser
ablation of layered semiconductors. Rapid evaporation of material provoked by high intensity
laser beam creates favorable conditions for cluster formation. Recent success in investigations
of new ultra-stable material compositions [1] led us to search for clusters with elevated stability
of other materials.
Films consisting of HgI2 and PbI2 nanoparticles (NP) have been prepared by pulsed N2 laser
ablation. Absorption spectrum shows one broad peak of HgI 2 NP and one peak of PbI 2 NP
corresponding to wide size distribution. Photoetching technique was used to decrease number of
large particles. Strong blue shift of PL peak of NP film caused by quantum size effect is
observed (Fig.1). Semi-empirical structure calculations were performed using the MNDO basis
set in the GAMESS package. The calculation shows that there are few stable clusters of HgI2
and PbI2 with atomic masses less than 4000 a.m.u. To confirm theoretical calculations mass
spectra of samples of HgI2 (Fig. 2) and PbI2 are obtained. Samples for mass-spectroscopy were
prepared at similar conditions and in the same manner as for optical investigations. Peak
positions correspond to stable clusters of both materials HgnIm and PbnIm consisting of n = 3, m
= 5; n = 4, m = 7; n = 4, m = 9 atoms. There is a good agreement of theoretical prediction and
observed peaks in mass spectra.
Figure 1. Photoluminescence spectrum of HgI2
stable clasters. Narrow line at 540nm
corresponds to emmision of nanoparticles.
References
Figure 2. Mass-spectrum of HgnIm clusters
prepared by laser ablation. Numbers in brackets
corresponds to assigned number of atoms of Hg
and I, respectively.
[1] A.Kasuya, R.Sivamohan, Yu.Barnakov, I.Dmitruk, et al, Nature Materials, No.3 (2004).
85

B - 41
Stable Cluster Motifs For Nanoscale Materials
S. N. Khanna
Physics Department, Virginia Commonwealth University, Richmond, Va. 23284-2000, USA
A major step in creating nanoscale materials with desirable electronic and magnetic
properties is the identification of structural motifs that can simultaneously display the stability
requisite for implementation as building blocks and the preservation of electronic and magnetic
properties within this motif. Using three different examples (marking different bonding
characteristics), we present our recent results on how by controlling size, composition and
formation conditions, it may be possible to design very stable clusters with desirable traits that
could serve as the building blocks for extended materials.
The first part of the work concerns our recent investigations on chromium and iron oxide
clusters. We have shown that by controlling the formation conditions, it is possible to generate
different classes of metal-oxide clusters, each with unique electronic and magnetic properties. In
particular, size-selected iron-oxide clusters can oxidize CO and reduce NO and offer
tremendous potential for applications [1].
The second part of the work concerns our recent investigations on aluminum halogen clusters. It
is shown that some of the acid etching reactions that can lead to very stable aluminum halogen
mixed clusters. The studies provide evidence that Al13 - can act as a superhalogen when
combined with conventional halogens. What is truly remarkable is that a completely new class
of poly-halides can be formed by using Al13 - in combination with conventional halogens [2].
Finally, we have just extended our previous work on semiconductor metal clusters [3]. We have
re-examined some of rules that govern the stability of this important class of clusters and found
that the metal-semiconductor bonding obeys simple electron counting rules. Needless to say,
these rules can guide the search of new stable clusters.
References
[1] B. V. Reddy and S. N. Khanna, Phys. Rev. Lett. 93, 068301 (2004).
[2] D. E. Bergeron, A. W. Castleman, Jr., T. Morisato and S. N. Khanna, SCIENCE 304, 84 (2004); D.
E. Bergeron, P. J. Roach, A. W. Castleman, Jr., N. O. Jones, and S. N. Khanna, SCIENCE
(Submitted).
[3] S. N. Khanna, B. K. Rao, and P. Jena, Phys. Rev. Lett. 89, 016803 (2002).
86

Passivation, charging and optical properties of gold nanoclusters
Hannu Häkkinen
Department of Physics, Nanoscience Center, University of Jyväskylä, Finland
B - 42
Nanoclusters and nanoparticles are currently a subject of intense experimental and
theoretical research efforts due to their unique physical and chemical properties that might be of
potential use in future nanotechnologies. The properties of Gold nanoclusters are extraordinary
sensitive to a number of factors, including size, charge state, passivation by inorganic ligands,
and the type and amount of impurity atoms. Varying these factors allows one to "tune" or
"functionalize" the electrical, optical and chemical properties in a desired way. This contribution
will discuss phosphine- and thiol-passivated WAu12, Au39 and Au55 clusters in light of recent
large-scale density functional simulations. It is shown that the properties of the gold core can
easily be controlled by changing the ligand from π-acidic to σ-donating, i.e., by “chemical
charging”. Exchange of phosphine ligands to CO molecules is energetically possible for some
of the clusters, making them interesting candidates for nanocatalysts for CO oxidation.
Figure 1. Spacefill visualization of trimethylphosphine-passivated Au 55 chloride Au 55(PMe 3) 12Cl 6 – a model for the
famous “Schmid cluster” (ref. 1).
References
[1] G. Schmid, Chem. Rev. 92, 1709 (1992).
87

B - 43
88
Deposition of Magic Silicon Clusters
Rainer Dietsche, Felix von Gynz-Rekowski, Dong Chan Lim, Nils Bertram, Tim Fischer,
Ignacio Lopez-Salido, Young Dok Kim, and Gerd Ganteför
Fachbereich Physik, Universität Konstanz, 78457 Konstanz, Germany.
http://www.clusterphysik.uni-konstanz.de/
Since the discovery of the “supermagic” cluster C60 [1] researchers are fascinated by the
possibility to synthesize new materials consisting of stable clusters. Aiming this question we are
investigating small Silicon clusters and evaluating whether these clusters might be suitable as
building blocks for cluster materials. Previous studies on mass-selected cluster anions of Silicon
suggests, that clusters containing 4, 6, 7, and 10 Silicon atoms are closed-shell species with
band gaps of 1 to 1.5 eV [2][3] indicating relatively inert and stable properties of these clusters.
In our experiment “magic” Silicon clusters Si4 and Si7 are produced by a magnetron sputter
source, mass selected and soft landed (Ekin ≤ 0.3 eV/atom) on Highly Oriented Pyrolytic
Graphite (HOPG), amorphous Carbon and Silver. The deposited clusters are studied via
Ultraviolet Photoelectron Spectroscopy (UPS), X-Ray Photoelectron Spectroscopy (XPS), Low
Energy Electron Diffraction (LEED), Auger Electron Spectroscopy (AES) and High-Resolution
Electron Energy Loss Spectroscopy (HREELS). The results are compared to those of “nonmagic”
clusters like Si8 and Silicon bulk.
The experimental data indicates that “magic” Silicon clusters do not form bulk material upon
deposition whereas Silicon monomers show bulk like electronic structures. Furthermore the
deposited clusters show no significant reactivity towards Oxygen. However, additional
measurements have to be made.
References
[1] H. W. Kroto, J. R. Heath, S. C. O’Brien, R. F. Curl, and R. E. Smalley, Nature 318, 162 (1985).
[2] O. Cheshnovsky, S. H. Yang, C. L. Pettiette, M. J. Craycraft, Y. Liu, and R. E. Smalley, Chem.
Phys. Lett. 138, 119 (1987).
[3] J. Müller, B. Liu, A. A. Shvartsburg, S. Ogut, J. R. Chelikowsky, K. W. M. Siu, K.-M. Ho, and G.
Ganteför, Phys. Rev. Lett. 85, 1666 (2000).

WS and MoS: Magic Clusters and Nanoplatelets studied by PES
N. Bertram, J. Cordes, Young Dok Kim, G. Ganteför
Department of Physics, University of Konstanz, 78457 Konstanz, Germany.
http://www.clusterphysik.uni-konstanz.de/
B - 44
MoS and WS are very similar to carbon in the bulk. Thus it is interesting to see whether
layered structures or even fullerenes can be formed out of these materials in the nano-regime.
For WS clusters, a series of stable triangular platelet structures has been predicted by theory
[1] consisting of 6, 10, 15 etc. W atoms forming the plane of the triangle and a corresponding
number of S atoms located on both sides. WS clusters have now been generated in the PACIS
source and studied by means of mass spectroscopy and photoelectron spectroscopy (PES),
supporting the platelet hypothesis. The platelets show an electron affinity around 4 eV and, in
agreement with theory, no electronic gap.
In addition to that, several smaller magic MoS and WS cluster have been studied and very
large electronic gaps (~ 2 eV) have been found for Mo4S6 and W4S6 for example, indicative of a
high stability. For MoS, Chevrel phases have been observed, consisting of Mo6S8 building
blocks. Due to their high stability, the aforementioned magic clusters are very promising
building blocks for deposition on surfaces and the formation of cluster materials.
References
Figure 1. Measured photoelectron spectrum of W 4S 6 - and calculated structure of Mo4S 6 - by G. Seifert.
Figure 2. Calculated structure of MoS-platelet by G. Seifert and Chevrel phase consisting of Mo 6S 8.
[1] Gotthard Seifert, Institute for Physical Chemistry, Technical University Dresden, 01062 Dresden,
Germany.
89

Methods
91

PEACE - a new photoelectron action spectroscopy
Shai Ronen, Israel Wolf, Rina Giniger and Ori Cheshnovsky
School of Chemistry, the Sackler Faculty of Exact Sciences,
Tel Aviv University, Tel Aviv 69978 Israel
B - 45
Neumark and coworkers [1] have pioneered ZEKE spectroscopy on anionic molecules and
clusters. Unfortunately, due to the low cross-section for electron detachment of anions at
threshold, this method is very difficult to apply.
We present a new experimental approach, in which the action spectroscopy is recorded with
electrons of fixed finite kinetic energy. This approach circumvents some shortcomings of the
anionic ZEKE. By working above threshold the cross-section is higher, allowing for higher
signal, and the detection of electrons with l>s angular momentum. Neumark and coworkers
have recently developed an equivalent technique based on the velocity map imaging.[2]
The method is based on a modified Magnetic Bottle Photoelectron spectrometer (MBPES). A
tunable laser is used to detach electrons from mass selected anions, which move collinearly with
the 50 cm MBPES drift tube. To avoid Doppler broadening, a low voltage pulse removes the
velocity component of anions from the detached electrons[3]. 20 cm downstream, after the
parallelization of the electrons in the drift tube, another pulse is applied to reduce their velocity
by a fixed amount. The spectrum is collected by recording the wavelength dependence of
electron-signal at a predetermined TOF window. This arrival time corresponds to a specific
electron-kinetic energy. We have chosen to call this approach PEACE, denoting PhotoElectron
Action spectroscopy at Constant kinetic Energy.
Our best resolution so far is 1 meV for 10 meV electrons. Below we demonstrate a PEACE
spectrum of HgCl- together with the corresponding simulated theoretical spectrum.
References:
600
500
400
300
200
100
0
600
500
400
300
200
100
0
0-12
1-13
Simulated Spectrum
Observed Spectrum
27000 27500 28000 28500 29000 29500 30000 30500
Energy [cm -1 ]
[1] T.N. Kitsopoulos, I. M. Walker, J.G. Loser, D.M. Neumark, Chem. Phys. Letters 159 300 (1989)
[2] Osterwalder, M. J. Nee, J. Zhou, and D. M. Neumark, J. Chem. Phys. 121, 6317 (2004).
[3] R. Giniger T. Hippler, S. Ronen, O. Cheshnovsky, Rev. Sci. Instrum. 72, 2543 (2001)
93

B - 46
94
The effect of cluster-gas collisions on the averages of charge, energy
and mass of an Ar gas cluster ion beam and implications for cluster
induced surface modifications
D. R. Swenson
Epion Corporation, Billerica, MA 01833 USA
Cluster-gas collisions have been the subject of several recent papers, but there have been no
studies for large, multi-charged clusters that are typical of commercial Gas Cluster Ion Beams
(GCIB). For such large clusters the standard techniques are not adequate because they measure
m/q ratios leaving the mass and charge ambiguous. In a recent paper I reported the first
measurements of charge state q, energy E, and mass m for very large Ar clusters as are
commonly used in GCIB processing of surfaces [1]. In that paper the average charge of the
I
clusters was determined by q = , where I is the electrical current measured by a Faraday
αeΓ
cup, Γ is the flow rate of particles in the beam, as measured using a modified Daly detector and
applying particle counting techniques, and α was the measured relative detection efficiency.
The experimental apparatus also included TOF and electrostatic spectrometer measurements, all
for the same pico-amphere-level sample of a high intensity Ar GCIB that was accelerated with
30 kV accel potential. This so named “QEM” technique was used to look for the presence of
multiply charged clusters in the beam and to study the effect of cluster-gas collisions. The data
from the experiment consists of measurements of q , and spectra of velocity v and E/q that were
measured for various thicknesses of Ar gas that was introduced into a cell immediately
upstream of the instruments. The averages v and { E q}
ave are determined from the spectra,
2E
and averages of cluster mass and energy are given by E = q{
E q}
ave and by m = . The 2
v
derived averages are strictly valid if the various distributions are uncorrelated. In this paper I
further analyze the data from this experiment and show that a simple analytical model can
predict the main features of the data. A more detailed Monte-Carlo simulation is also compared
to the results and to the analytical model, and it is used investigate the limitations of the
experimental technique, particularly to what degree correlations affect the average values
derived using the QEM technique. The clusters studied had averages of +3.2 charges, 64 keV
energy, and 10,400 atoms at the lowest gas target thickness and were progressively abraded as
the target thickness was increased. It is shown that the mass loss is consistent with a simple
theory that assumes thermalization of the collision energy followed by evaporation.
Surprisingly, the clusters lose mass at a greater rate than charge and the N/q ratio decreases as a
result of gas collisions. The measurements are important for cluster-surface interactions because
they allow cluster energy and dose to be measured for multi-charged clusters. The theory
developed can be used to understand, predict and optimize the effect of gas-cluster collisions on
cluster-surface processing.
References
[1] D.R. Swenson, Nucl. Instr. and Meth. B 222 (2004) 61

B - 47
Computational Electron Spectroscopy – A Powerful Tool for Studies of
Clusters
Julius Jellinek
Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, USA
A new highly accurate scheme for computation of the electron energy spectra within the
density functional theory [1] will be sketched, and the results of its application to one- and twocomponent
metal clusters will be presented and analyzed. The analysis will include the
evolution of the spectra with the cluster size [2-4], structure [4-5], charge state [2-4], and
composition [6]. The computed results will be compared with the available experimental data
[7,8], and their role in the interpretation of these data will be illustrated. The discussion will
include analysis of the phenomenon of size-induced nonmetal-to-metal transition, which defines
the limits of miniaturization in nanoelectronics, and the possible relationship between this
phenomenon and the photonic and catalytic properties of clusters/nanoparticles.
References
[1] J. Jellinek and P. H. Acioli, J. Chem. Phys. 118, 7783 (2003).
[2] P. H. Acioli and J. Jellinek, Phys. Rev. Lett. 89, 213402 (2002).
[3] J. Jellinek and P. H. Acioli, J. Phys. Chem. A 106, 10919 (2002); 107, 1670 (2003).
[4] J. Jellinek and P. H. Acioli, in Metal Ligand Interaction in Molecular-, Nano- and Macro-Systems
in Complex Environments, N. Russo, D. R. Salahub, and M. Witko (Eds.), Kluwer Academic
Publishers, Dordrecht, 2003, p. 121.
[5] P. H. Acioli and J. Jellinek, Eur. Phys. J. D 24, 27 (2003).
[6] P. H. Acioli and J. Jellinek, to be published.
[7] O. C. Thomas, W. Zheng, S. Xu, and K. Bowen, Phys. Rev. Lett. 89, 213403 (2002).
[8] L.-S. Wang et al., to be published.
95

B - 48
96
Carbon clusters for the calibration in mass spectrometry
Alexander Herlert 1,2 , Sudarshan Baruah 1 , Klaus Blaum 3,4 , Michael Block 4 ,
Ankur Chaudhuri 1 , Frank Herfurth 4 , Alban Kellerbauer 2 , H.-Jürgen Kluge 4 ,
Gerrit Marx 1 , Mannas Mukherjee 4 , Lutz Schweikhard 1 , and Chabouh Yazidjian 2,4
for the ISOLTRAP and SHIPTRAP collaboration
1 Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, 17487 Greifswald, Germany
2 CERN, Department of Physics, 1211 Geneva 23, Switzerland
3 Institut für Physik, Johannes Gutenberg-Universität Mainz, 55099 Mainz, Germany
4 GSI, Planckstr. 1, 64291 Darmstadt, Germany
The masses of radionuclides are of importance in a wide range of physics branches [1]:
From nuclear structure studies to tests of the Standard model. Penning traps have proven to
allow the mass determination of short-lived nuclides with a relative mass uncertainty of less
than δm/m=1·10 -8 [2,3] and in case of stable nuclides even below 2·10 -11 [4,5].
The principle of accurate mass measurements is based on the precise determination of the
cyclotron frequency νc=qB/(2πm) of the stored ions in the trap. The experimental scheme
monitors the gain in kinetic energy of the radial ion motion after excitation with a quadrupolar
radiofrequency field [6]. For the determination of the ion mass, the magnetic field needs to be
calibrated. This is achieved with the measurement of the cyclotron frequency of an ion with
well-known mass. Here, carbon clusters are the reference particles of choice. First, the mass of a
12 C atom defines the atomic mass unit. Second, with respect to their mass, carbon clusters Cn are
distributed like a grid on the chart of nuclides, where the maximum distance of any nuclide to a
carbon cluster is six atomic masses.
In addition, cross-reference measurements allow consistency checks. Thus, carbon clusters
have been used to determine the systematic uncertainties in the mass determination of very
short-lived nuclides [7] at the triple trap mass spectrometer ISOLTRAP [8] at ISOLDE/CERN.
For these studies the clusters were produced by laser ablation from a Fullerene target [9]. A new
carbon cluster ion source has recently been installed and will be tested for the upcoming beamtime
period at ISOLDE/CERN. A similar cluster ion source is presently being installed at the
mass spectrometer SHIPTRAP [10] at GSI, which is devoted to mass spectrometry of superheavy
nuclides that are delivered from the mass separator SHIP. First results are presented.
References
[1] D. Lunney et al., Rev. Mod. Phys. 75, 1021 (2003).
[2] G. Bollen, Eur. Phys. J. A 15, 237 (2002).
[3] M. Mukherjee et al., Phys. Rev. Lett. 93, 150801 (2004).
[4] R.S. van Dyck et al., Phys. Rev. Lett. 92, 220802 (2004).
[5] S. Rainville et al., Science 303, 334 (2004).
[6] M. König et al., Int. J. Mass Spectrom.Ion Proc. 142, 95 (1995).
[7] A. Kellerbauer et al., Eur. Phys. J. D 22, 53 (2003).
[8] F. Herfurth et al., J. Phys. B: At. Mol. Opt. Phys. 36, 391 (2002).
[9] K. Blaum et al., Anal. Bioanal. Chem. 377, 1133 (2003).
[10] G. Marx et al., Hyperfine Interact. 146/147, 245 (2003).

Photoionisation using Kohn-Sham wave functions
Michael Walter and Hannu Häkkinen
Department of Physics, Nanoscience Center, University of Jyväskylä, Finland
B - 49
The determination of photoionisation cross sections using the Kohn-Sham wave functions
from accurate DFT calculations is studied. The continuum electron is described by an analytical
wave function and the matrix elements are calculated in both in length and velocity form of the
dipole operator. The test case of water shows excellent agreement between the calculations and
experiment in the ionisation energies if a vertical transition is considered. The cross sections
agree well with the experiment in particular in case of the velocity form results. Differences to
the length form and deviations from the experimental asymmetry parameters indicate the
limitations in an analytical description of the continuum [3].
Figure 1. State resolved photoionisation cross sections in velocity (full line) and length form (dotted line) for the two
states with the lowest binding energy of water. Experimental data from [1] (boxes and triangles) and [2] (circles).
References
[1] M. S. Banna et al, J. Chem. Phys. 84, 4789 (1986).
[2] C. M. Truesdale et al, J. Chem. Phys. 76, 860 (1982).
[3] M.Walter and H. Häkkinen, submitted to Phys. Rev. A
97

B - 50
98
Investigation of cluster ions in a Paul trap
Franklin Martinez 1 , Alexander Herlert 1,2 , Gerrit Marx 1 , Hagen Ritter 1 , Lutz Schweikhard 1
1 Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, 17487 Greifswald, Germany
2 CERN, Department of Physics, 1211 Geneva 23, Switzerland
The storage of cluster ions in a Penning trap has proven to allow various possibilities of
experimental investigation [1,2,3,4]. The advantage of only an upper but no lower mass limit
and thus trapping of particles within a large mass range (even electrons and comparatively
heavy cluster ions) has to be paid by the limitation to only one charge-state polarity and a
reduced access to the stored ions since the Penning trap is mounted inside the bore of a
superconducting magnet.
The Paul trap or radiofrequency trap does not need the strong magnetic field but uses a timevarying
quadrupolar electric field. This allows the storage of positively and negatively charged
particles at the same time. In addition the rf trap can be constructed very compact and with
relatively open trap electrodes and therefore axial as well as radial access to the trap is relatively
easy. As an example, a Paul trap has been successfully applied by Parks and coworkers for
electron-diffraction measurements [5].
In the framework of experiments on stored clusters similar to the ClusterTrap measurements [1],
the application of a Paul trap for future cluster studies is investigated. In a first study the
storage, manipulation and detection of atomic clusters are tested. The trapping of fullerenes of
either charge state and their interaction with electrons, ions, neutral atoms as well as photons
will be investigated. The new experimental setup and first results will be presented.
References
[1] L. Schweikhard et al., Eur. Phys. J. D 24, 137 (2003).
[2] C. Walther et al., Phys. Rev. Lett. 83, 3816 (1999).
[3] C. Yannouleas et al., Phys. Rev. Lett. 86, 2996 (2001).
[4] M. Vogel et al., Phys. Rev. Lett. 87, 013401 (2001).
[5] S. Krückeberg et al., Phys. Rev. Lett. 85, 4494 (2000).

Structural characterization of large molecules and clusters by
photofragmentation spectroscopy and scattering experiments.
Michalis Velegrakis
Foundation for Research & Technology – Hellas (FORTH),
Institute of Electronic Structure and Laser (IESL)
P.O. Box 1527, Heraklion, GR 71110, Crete
B - 51
The rapid progress in molecular beam techniques, in combination with lasers in the last
years, allowed the production of novel molecules in the gas phase such as atomic clusters, metal
oxides and complexes between metal ions and biomolecules. There is growing interest in
obtaining structural information for these molecules.
In this contribution, recent results obtained in the Molecular Dynamics & Clusters laboratory at
IESL are presented. Using a molecular beam apparatus equipped with a time–of-flight massspectrometer,
charged clusters are produced in an ion-source which is based on the combination
of laser ablation and supersonic gas-expansion.
Mass-spectroscopy, photofragmentation spectroscopy of mass-selected ions and molecular
beam scattering techniques with the aid of theoretical models are employed in order to infer the
stability and the structure of these molecules.
99

Metals
101

A - 0
102

Size, charge, and isomer specific vibrational spectroscopy of isolated
metal clusters
André Fielicke 1 , Christian Ratsch 1,2 , Gert von Helden 1 , and Gerard Meijer 1
1 Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin, Germany
2 Department of Mathematics, UCLA, Los Angeles, CA 90095-1555, USA
A - 1
We report on the vibrational spectra of neutral and charged metal clusters in the far infrared.
These spectra are obtained via far infrared resonance enhanced multiple photon dissociation
(FIR-MPD) of the complexes of metal clusters with rare gas atoms. The experiments make use
of the Free Electron Laser for Infrared eXperiments FELIX in Nieuwegein, The Netherlands, as
an intense and widely tunable far-infrared radiation source.
The measured FIR-MPD spectra of the complexes represent the infrared absorption spectra of
the bare metal clusters. These spectra are unique for each cluster size and are true fingerprints of
the cluster’s structure. This FIR-MPD technique has been applied to cationic vanadium clusters
[1] and cationic and neutral niobium clusters containing 3 to more than 20 atoms. Interestingly,
for some cluster sizes, the vibrational spectra of neutral and cationic niobium clusters differ
rather strongly, indicating different geometric structures. For smaller sized clusters (n

A - 2
104
Gold Clusters with Density-Functional Based Tight-Binding Method
Pekka Koskinen 1 , Hannu Häkkinen 1 , Gotthard Seifert 2 , and Michael Moseler 3
1 Department of Physics, NanoScience Center, 40014 University of Jyväskylä, Finland
2 Institut für Physikalische Chemie, TU Dresden, Mommsenstrasse. 13, 01062 Dresden, Germany
3 Fraunhofer Institut für Werkstoffmechanik, Wöhlerstrasse 11, 79108 Freiburg, Germany
In this work we employ the density-functional based tight-binding method (DFTB)[1] in the
study of structures and energies of neutral and charged gold clusters. These clusters have been
studied extensively with the density-functional approach (DFT), but for clusters of larger size or
for molecular dynamics simulations of more complex structures one should have a more
efficient yet accurate computational tool. In this work we demonstrate that this efficient method
might indeed be a useful tool in the study of gold clusters.
As an example, Fig. 1 shows the reproducibility of the relative energies of the isomers of Au - 7clusters,
as compared with previous DFT studies [2]. Even better than the energy, the method
gives mainly the same stable cluster geometries as density-functional calculations. The
electronic structure is well described, as can be seen in the vertical detachment energies in Fig 2.
The DFTB-method is able to show that the structure of the ground state of small gold anions
transforms from two-dimensional to three-dimensional at approximately correct cluster size. We
studied larger Au - 55-cluster isomers and found the same stable structures compared to previous
studies, as well as reasonable isomer energies [3].
Fig.1 Energies and structures of a few Au - 7-clusters.
The energies are calculated with self-consistent
charge (SCC) DFTB as well as with DFT and plotted
relative to the corresponding ground state.
References
Fig. 2 The vertical detachment energies of the Au - 7clusters
shown. The values are consistently lower
than gradient-corrected DFT (GGA), and the error is
of the same order than with local-density DFT
(LDA).
[1] M. Elstner, D. Porezag, G. Jungnickel, J. Elstner, M Haug, Th. Frauenheim, S. Suhai, and G.
Seifert, Phys. Rev. B 58, 7260 (1998).
[2] H. Häkkinen, M. Moseler, and U. Landman, Phys. Rev. Lett. 89, 033401 (2002).
[3] H. Häkkinen, M. Moseler, O. Kostko, N. Morgner, M.A. Hoffmann, and B.v.Issendorff, Phys. Rev.
Lett. 93, 093401 (2004)

A - 3
Structure, energetics, and thermodynamics of copper, nickel, and gold
clusters: N = 2–150
V. G. Grigoryan, D. Alamanova, and M. Springborg
Universität des Saarlandes, Physikalische und Theoretische Chemie, Postfach 151150
D-66041 Saarbrücken, Germany
The three most stable structures of CuN, NiN, and AuN clusters with N between 2 and 150
have been determined using a combination of the Embedded-Atom (EAM), the quasi-Newton,
and our own [1-3] Aufbau/Abbau methods for calculations of the total energies, local and global
minima, accordingly. We have employed two well-known versions of the EAM: (1) the bulk
version of Daw, Baskes and Foiles and (2) the Voter-Chen version which takes into account
properties of the dimer. The lower-energy structures (also for the smallest ones) of CuN and NiN
clusters (structural details, symmetry and the ordering of the isomers) obtained with the two
versions are almost the same. Thus our study points to the universality of the bulk embedding
functions and potentials for copper and nickel at least for computations of structural properties.
But the bulk EAM fails completely to describe the structures of the smallest Au clusters. Hence
for the gold clusters only the Voter-Chen version of the EAM has been used. Copper and nickel
grow qualitatively similarly. Generally, we find a multilayered icosahedral or layer-by-layer
growth. But the cluster growth pattern between two closed-shell icosahedra is not simple. It is
predominantly icosahedral with islands of fcc, tetrahedral, and decahedral growth. Further, we
have observed an enhanced ability of fcc clusters to compete with icosahedral and decahedral
structures in the vicinity of N=79. The truncated centered octahedron at N=79 is the first and the
second lower-energy structures for Cu and Ni clusters, respectively. The derived results are
detailed discussed and compared with those of available ab initio and semiempirical studies.
Agreement with experimental studies is very good in many cases. The situation for gold is more
complicated. We could not detect any favored structural motif. For example, Au13 is the first
Mackay icosahedron, Au38 is the truncated octahedron, but all the three isomers for Au55 are
low-symmetric. Our result for 38-atom gold cluster agrees with the many-body Sutton-Chen and
Murrell-Mottram calculations, but it is in contradiction with the 'disordered' result of the n-body
Gupta potential. Hence more studies are needed. Furthermore, we determine the full vibrational
spectrum and the vibrational heat capacities (contributions from rotations are negligible) of
clusters for each cluster size. It is found, that the 23-atom Cu or Ni cluster (triple icosahedron)
possesses the highest vibrational frequency. Further it is shown that the highest vibrational
frequency is lower in the fcc and decahedral clusters and higher in the icosahedral ones. The
heat-capacity plots for low temperatures show very interesting fine structures with minima at
magic numbers of 13 and 55 and with a broad maximum in the vicinity of N=35.
References
[1] V. G. Grigoryan and M. Springborg, Phys. Chem. Chem. Phys. 3, 5125 (2001).
[2] V. G. Grigoryan and M. Springborg, Chem. Phys. Lett. 375, 219 (2003).
[3] V. G. Grigoryan and M. Springborg, Phys. Rev. B 70, 205415 (2004).
105

A - 4
Structure Determination of Small Silver Cluster Ions by Trapped Ion
Electron Diffraction
106
Detlef Schooss 1 , Martine N. Blom 1 , Lars Walter 1 , Mattias Kordel 1 , Jason Stairs 1 , Joel H. Parks 2 and
Manfred M. Kappes 1,3
1 Institute of Nanotechnology, Forschungszentrum Karlsruhe,D-76021 Karlsruhe, Germany
2 The Rowland Institute at Harvard, Cambridge, MA 02142, USA
3 Institut für Physikalische Chemie, Universität Karlsruhe, D-76128 Karlsruhe, Germany
The structure of silver clusters ions is studied by the recently developed technique of
trapped ion electron diffraction (TIED) [1]. In brief, cluster ions are generated by a magnetron
sputter source [2] and injected into a Paul ion trap. After mass selection and thermalization the
trapped ions are irradiated with a 40 keV electron beam and the resulting diffraction pattern is
integrated with a CCD detector. The sensitivity and resolution of the apparatus is documented
by figure 1 which shows the molecular scattering function obtained for Ag55 + at 90K.
+
Figure 1: Experimental diffraction pattern (open squares) of mass selected Ag55 at 90K. The measurement is
consistent with an icosahedral structure as calculated from RIDFT calculations (line).
Comparison to RIDFT structure calculations for various trial geometries reveals that the cluster
ensemble which was probed comprises predominantly icosahedral Ag55 + . TIED measurements
at different cluster sizes and charge states (Ag19 +/- to Ag79 +/- ) at a variety of temperatures ranging
from 100 - 650 K are presently ongoing.
References
[1] M. Maier-Borst, D. C. Cameron, M. Rokni and J. H. Parks, Phys. Rev. A, 59, R3162 (1998), S.
Krückeberg, D. Schooss, M. Maier-Borst, J. H. Parks, Phys. Rev. Lett. 85(21), 4494-4497 (2000)
[2] H. Haberland, M. Mall, M. Moseler, Y. Qiang, T. Reiners and Y. Thurner, J. Vac, Sci. Technol.
A 12(5), 2925 (1994)

Metal Cluster Anions Produced by Attachment of Slow Electrons:
Readjustment and Blurring of the Magic Numbers
R. Rabinovitch, R. Moro, C. Xia, V. V. Kresin
Dept. of Physics, University of Southern California, Los Angeles, California 90089-0484, USA
A - 5
The high electric polarizabilities of metal clusters enable them to attach low-energy
electrons with very large cross sections [1]: a passing electron is captured by a strong longrange
polarization potential. But very little is understood about the last stage of the collision
process: where and how fast is the captured electron’s energy deposited? The questions are
closely related to the general problem of electron relaxation in size-quantized nanoscale
systems.
To explore this issue, we are carrying out measurements of the mass spectra of negative sodium
cluster ions born in the electron-cluster interaction region. If the energy deposited by the
captured electron is quickly thermalized and is sufficient to cause rapid cluster evaporation,
there should result - a rearrangement of the cluster abundances and a shift of the magic numbers
Na
from Nan to n-1 .
In our experiment such a shift is clearly observed at shell closings near n=20 and n=40.
However, near n=58 and n=92 the shell closings become completely blurred (see Figure 1). This
interesting change may be due to a bottleneck in the electron relaxation and/or to insufficiently
fast evaporation. We will present the current data and discuss their implications.
This work was supported by the U. S. National Science Foundation.
Counts
500
450
400
350
300
250
200
150
100
References
Masscan of clusters Na18-Na21
Sm oothing
50
380 400 420 440 460 480 500
Mass, AMU
-
Counts
350
300
250
200
150
100
Masscan of clusters Na56-Na59
Sm oothing
1260 1280 1300 1320 1340 1360 1380
Mass, AMU
Figure 1. Mass spectra of Na (left) and Na (right) formed by electron attachment.
18-21
56-59
The shell edge is visible only in the first spectrum.
[1] V.Kasperovich, G.Tikhonov, K.Wong, and V.V.Kresin, Phys. Rev. A 62, 063201 (2000); Phys.
Rev. Lett. 85, 2729 (2000).
-
107

A - 6
108
Mass Spectrometric Investigations of Binary Clusters:
Evidence for Endohedral Clusters with Enhanced Stability
Peter Lievens, Ewald Janssens, Sven Neukermans, Xin Wang, Nele Veldeman, Roger E. Silverans
Laboratorium voor Vaste-Stoffysica en Magnetisme, K.U.Leuven,
Celestijnenlaan 200D, B-3001 Leuven, Belgium
While clusters composed of rare gas atoms exhibit enhanced stabilities when they have
magic numbers enabling them to adopt high symmetry geometries ("shells of atoms"), the magic
numbers in alkali and other simple metal clusters are determined by the number of delocalized
valence electrons occupying a one-particle state in a (centro-)symmetric potential well ("shells
of electrons"). The quest for such electronically and geometrically closed shells, which goes
along with enhanced cluster stability, has been a leading thread in cluster research for many
years. One route has been the investigation of binary clusters, which allows tailoring both the
cluster geometry (number of atoms) and electronic properties (number of delocalized electrons)
independently.
We produce beams of binary clusters with a dual-target dual-laser vaporization cluster source,
and investigate the clusters in the gas phase with mass spectrometric and laser spectroscopic
techniques. In particular, size and composition dependent stability fluctuations are investigated
with photofragmentation and mass spectrometry, and size dependent ionization energies are
measured with threshold laser ionization spectroscopy.
Lately we focussed on investigations of two types of bimetallic systems: clusters consisting of
noble metals doped with transition metal atoms, and clusters of group IVa elements doped with
metal atoms [1-3]. In this contribution we will present evidence for the existence of combined
closures of shells of atoms and shells of electrons for specific binary cluster species.
Phenomenological interpretations of new electronic shell closures enhanced by size specific
geometry considerations will be given based on comparisons with density functional theory
calculations. In particular the formation of stable icosahedral 13 atom systems with the dopant
atom occupying a central position will be highlighted. Also, size dependent magnetic properties
of endohedral clusters with a magnetic atom occupying a central position will be discussed.
This work was supported by the Fund for Scientific Research – Flanders (FWO), the Flemish
Concerted Action (GOA) program, and the Belgian Interuniversity Poles of Attraction (IAP)
program. EJ and SN are Postdoctoral Researchers of the FWO.
References
[1] S. Neukermans, E. Janssens, H. Tanaka, R.E. Silverans, P. Lievens, Phys. Rev. Lett. 90 (2003)
#033401.
[2] E. Janssens, H. Tanaka, S. Neukermans, R.E. Silverans, P. Lievens, New J. Phys. 5 (2003) #46.
[3] S. Neukermans, E. Janssens, Z. Chen, R.E. Silverans, P.v.R. Schleyer, P. Lievens, Phys. Rev. Lett.
92 (2004) #163401.

Photoelectron spectrometry of big sodium clusters
Oleg Kostko and Bernd von Issendorff
Fakultät für Physik, Universität Freiburg, H.Herderstr. 3, 79104 Freiburg, Germany
A - 7
We have measured photoelectron spectra (PES) of Na – n clusters with n=5-4000 at a photon
energy of 4.02 eV. For the smaller sizes (n=5-480) a liquid nitrogen cooled rf-octupole trap was
used for thermalization and intensity bunching. Bigger clusters were examined without
additional thermalization. The estimated temperature of the clusters in both cases was about
100 K. Comparison of the PES obtained this work with data published earlier [1,2] shows that
the lower temperature leads to significantly better spectral resolution and in some cases to a
change of the shape of the spectra.
In the PES of the bigger clusters a periodic vanishing and appearing of structure was observed.
For instance Na – 730 and Na – 1250 exhibit almost unstructured spectra, while Na – 670 and Na – 1350
exhibit rather structured spectra. The reason for this behaviour seems to be a combination of
geometrical shell closing and electronic supershell modulation.
From the measured photoelectron spectra the electron affinities of the anions and the ionization
potentials of the neutrals were extracted. These values are plotted in Fig.1 as a function of N -1/3 .
Their difference yields the cluster charging energy, which can be used to determine the Wigner-
Seitz radius of sodium (Rws) and the electron spillout (δ). In our case values of 2.07 Å and
0.97 Å were obtained, respectively. The literature value for Rws of bulk sodium at 100 K is
2.08 Å. Fitting the electron affinity and ionization potential curves according to the charged
droplet model
2
e
IP = WF + α 1/
3
R N + δ
additionally yields the parameter α=0.377 and the work function WF=2.84 eV, which is slightly
higher then the literature value of 2.75 eV.
EA and IP, eV
4
3
2
1
IP
EA
0.0 0.1 0.2 0.3
N
0.4 0.5 0.6
-1/3
Figure 1. Electron affinity and ionization potential as a function of the inverse of the cubic root of the cluster size.
References
2,84 eV
α=0.377
δ=0.974Å
R =2.072Å
ws
[1] G.Wrigge, M.Astruc Hoffmann and B.v.Issendorff, Phys. Rev. A 65, 063201 (2002).
[2] M.Moseler, B.Huber, H.Häkkinen, U.Landman, G.Wrigge, M.Astruc Hoffmann and
B.v.Issendorff, Phys. Rev. B 68, 165413 (2003).
WS
109

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110
Probing the properties of polyanionic clusters in a Penning trap
Alexander Herlert 1,2 , Andreas Lassesson 1 , Franklin Martinez 1 , Gerrit Marx 1 ,
Lutz Schweikhard 1 , Noelle Walsh 1
1 Institut für Physik, Ernst-Moritz-Arndt-Universität Greifswald, 17487 Greifswald, Germany
2 CERN, Department of Physics, 1211 Geneva 23, Switzerland
Highly negatively charged clusters have attracted much interest within the last ten years [1]
and their study has led to the development of a new field in cluster research. The addition of
further electrons to an already negatively charged system is in itself an experimental challenge,
especially with respect to the stability of the polyanionic products. Furthermore, the additional
negative charges may lead to a change in the dissociation processes after excitation of the highly
charged clusters.
With the application of a Penning trap for the simultaneous storage of low-energy electrons and
singly-charged metal-cluster anions, the production of polyanionic metal clusters is reproducible
under controlled conditions [2]. Size-selected metal cluster dianions as well as trianions are
readily available for further investigation. First experiments concentrated on the relative yield of
the polyanionic metal clusters as a function of cluster size. The results are related to the second
electron affinity of the clusters including electronic shell effects [3].
Further investigations involved the excitation of the metal cluster dianions with photons and
also by collisions with inert gas atoms. Both methods were already established at the
ClusterTrap experiment [4]. In the case of collisional activation, the dianions are brought to a
larger cyclotron radius to increase their kinetic energy. After the collision with argon gas atoms
the emission of the surplus electron from the cluster was observed, but the change of the massover-charge
ratio led to a change of the ion motion and thus to the loss of the product ions [5].
For photoexcitation, the dianions were centered in the Penning trap and electron emission as
well as dissociation was observed in case of gold-cluster dianions [6]. The data is currently
being analyzed with respect to direct and thermionic electron emission.
In addition to the experiments on polyanionic metal clusters, the investigation of highly charged
fullerene anions has started. A new ion source for the ClusterTrap experiment has been
constructed that allows the production of both positively and negatively charged fullerenes.
Attachment of additional electrons to the singly charged fullerene anions has been successful
and dianions Cn 2- in the size range n ≥ 70 were observed. First results of the production and
further investigation of the size- and charge-state selected fullerene dianions will be presented.
References
[1] A. Dreuw and L.S. Cederbaum, Chem. Rev. 102, 181 (2002).
[2] A. Herlert and L. Schweikhard, Int. J. Mass Spectrom. 229, 19 (2003).
[3] C. Yannouleas et al., Phys. Rev. Lett. 86, 2996 (2001).
[4] L. Schweikhard et al., Eur. Phys. J. D 24, 137 (2003).
[5] A. Herlert and L. Schweikhard, Int. J. Mass Spectrom. 234, 161 (2004).
[6] L. Schweikhard et al., Int. J. Mass Spectrom. 219, 363 (2002).

Geometric and electronic tructure of large sodium cluster anions
Michael Moseler 1,2 , Bernd Huber 2 ,B. von Issendorff 3
1 Fraunhofer Institut für Werkstoffmechanik, Wöhlerstrasse 11, 79108 Freiburg, Germany
2 Freiburger Materialforschungszentrum , Stefan-Meier-Strasse 21, 79104 Freiburg, Germany
3 Fakultät für Physik, Universität Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Germany
A - 9
Photoelectron spectroscopy is a frequently used experimental method to extract electronic
binding energies from atomic, molecular, and condensed-matter systems. For molecules and
clusters at low temperature, a comparison of the measured photoelectron spectra (PES) with the
electronic density of states (DOS) obtained from density functional calculations for T=0 optimal
structures, provides information about the underlying electronic structure and may lead to
assignments of pertinent structures.
For the range of N=4-19 the PES of NaN - clusters were compared with the DOS recorded in our
finite-temperature ab initio simulations [1]. Although the main features of the PES can be
understood through the use of the jellium model, we are able to detect and explain several
spectral details caused by the finite temperature dynamics. Meanwhile experimental spectra
from very cold cluster beams are available and a comparison with T=0 static spectra reveals
new information concerning the ground states of the clusters.
Also larger sodium cluster anions have been measured and simulated by us. For Na55 -, Na147 -
and Na309 - the DOS of Mackay-icosahedral clusters was in good agreement with the
corresponding PES (see Fig. 1) and for Na71 - a clear difference between the DOS of an anti-
Mackay and an Mackay over layer has been detected.
References
Figure 1. Comparision of the Na309 - PES and the DOS of the Mackay-icosahedron.
[1] M. Moseler, B. Huber, H. Häkkinen, U. Landman, G. Wrigge, M. Astruc Hoffmann and B. von
Issendorff, Phys. Rev. B 68, 165413 (2003).
111

A - 10
112
Planar Boron Clusters and 2D to 3D Transitions
Hua-Jin Zhai, 1,2 A. N. Alexandrova, 3 B. Kiran, 1,2 S. Bulusu, 4 Jun Li, 2 Xiao Cheng Zeng, 3
A. I. Boldyrev, 3 and Lai-Sheng Wang 1
1 Department of Physics, Washington State University, 2710 University Drive, Richland, WA 99352, USA
and
2 W. R. Wiley Environmental Molecular Sciences Laboratory andChemical Science Division, Pacific
Northwest National Laboratory, P.O. Box 999, Richland, WA 99352, USA.
3 Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322-0300, USA
4 Department of Chemistry and Center for Materials Research and Analysis, University of Nebraska-
Lincoln, Lincoln, NE 68588, USA.
One of the most interesting features of elemental boron and many bimetallic boron
compounds is the occurrence of highly symmetric icosahedral clusters. The rich chemistry of
boron is also dominated by three-dimensional (3D) cage structures. We report our recent
investigations of small boron clusters in the size range from 3 to 20 atoms using photoelectron
spectroscopy and ab initio calculations [1-8]. We will present experimental and theoretical
evidence that small boron clusters prefer planar structures and exhibit aromaticity and
antiaromaticity according to the Hückel rules, akin to planar hydrocarbons up to the size of 19
atoms. Aromatic boron clusters possess more circular shapes whereas antiaromatic boron
clusters are elongated, analogous to structural distortions of antiaromatic hydrocarbons. In a
very recent study [8], we show that 3D structures begin at B20, which has a double ring global
minimum structure. The 2D to 3D structural transition observed at B20 suggests that it may be
considered as the embryo of the thinnest single-wall boron nanotubes.
References
B12 B13 B20
[1] H. J. Zhai, L. S. Wang, A. N. Alexandrova, and A. I. Boldyrev, J. Chem. Phys. 117, 7917-7924
(2002).
[2] A. N. Alexandrova, A. I. Boldyrev, H. J. Zhai, L. S. Wang, E. Steiner, and P. W. Fowler, J. Phys.
Chem. A 107, 1359-1369 (2003).
[3] H. J. Zhai, A. N. Alexandrova, K. A. Birch, A. I. Boldyrev, and L. S. Wang, Angew. Chem. Int. Ed.
42, 6004-6008 (2003).
[4] H. J. Zhai, B. Kiran, J. Li, and L. S. Wang, Nature Materials 2, 827-833 (2003).
[5] H. J. Zhai, L. S. Wang, A. N. Alexandrova, A. I. Boldyrev, and V. G. Zakrzewski, J. Phys. Chem.
A 107, 9319-9328 (2003)
[6] A. N. Alexandrova, A. I Boldyrev, H. J. Zhai, and L. S. Wang, J. Phys. Chem. A 108, 3509-3517
(2004).
[7] “Boron Flat Out” (S. K. Ritter), Chem. & Eng. News 82 (9), 28-32 (March 1 (2004).
[8] B. Kiran, S. Bulusu, H. J. Zhai, S. Yoo, X. C. Zeng, and L. S. Wang, Proc. Natl. Acad. Sci. (USA),
in press.

Molecular Clusters
113

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114

Molecular Beams of Organic Molecules
Tim Krause, Adnan Sarfraz, Wolfgang Christen
Institut für Chemie, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
A - 11
The transfer of non-volatile or thermally unstable molecules into the gas phase is of utmost
importance for a variety of applications such as analytical mass spectrometry, optical spectroscopy,
or the epitaxial growth of thin films. One possible method is the expansion of supercritical
solutions into a molecular beam. Here the key idea is to dissolve the substance at high
pressure, exploiting the supercritical fluid's solvent power, and precipitate it by expansion.
Extending our previous work on caffeine [1] and small molecules (vitamin K3, phenylalanine
tertbutylester) [2] we report the successful expansion of several molecules of biological interest
in supercritical CO2 at temperatures of only 310-315 K, and accompanying detection using mass
spectrometry.
References
[1] W. Christen, S. Geggier, S. Grigorenko, K. Rademann, Rev. Sci. Instrum. 75, 5048 (2004).
[2] W. Christen, T. Krause, H. Noack, A. Sarfraz, J. Chem. Phys., to be submitted.
115

A - 12
116
Infrared Spectroscopy of CO2 Containing Cluster Anions
Holger Schneider 1 , A. Daniel Boese 2 1, *
, J. Mathias Weber
1 Institut für Physikalische Chemie, Universität Karlsruhe, Kaiserstr. 12, 76229 Karlsruhe, Germany
* email: jmathias.weber@chemie.uni-karlsruhe.de
2 Institut für Nanotechnologie, Forschungszentrum Karlsruhe, Pstfach 3640, 76021 Karlsruhe, Germany
Molecular clusters are relevant model systems for the study of intermolecular interaction
potentials governing the structures of molecular complexes. Structural information on clusters
can be gained from infrared photodissociation spectroscopy in molecular beams [1, 2], and we
have applied this technique to several species, probing the interaction of various anions with
CO2. The experimental results are interpreted in the framework of density functional theory with
anharmonic calculations of vibrational spectra.
Halide-CO2 complexes afford the study of the interaction of CO2 with closed shell anions of low
reactivity [3]. The results are compared with those for Au - ·CO2 [4], which is relevant for the
study of catalytic oxidation of CO by gold clusters on surfaces [5, 6]. This complex shows
strong interaction between CO2 and the Au - anion, with a strongly deformed CO2 unit.
Complexes of O2 - with CO2 show very interesting motifs of ion solvation [7]. The π* orbital of
O2 - offers a template with four a priori equivalent binding sites for the structure of the
microsolvation environment. However, only one CO2 ligand is strongly bound, with additional
molecules weakly attached to the resulting CO4 - anion.
The general motif of anions binding to CO2 is binding to CO2 via the carbon atom, in contrast to
cations, which generally dock to one of the oxygen atoms. The geometry of the CO2 molecule is
changed upon complexation with the anion by electrostatic and charge transfer effects. Both
contributions deform the molecule away from the linear configuration of neutral CO2 towards
the bent anionic shape.
References
[1] W.H. Robertson and M.A. Johnson, Annu. Rev. Phys. Chem. 54 (2003) 173.
[2] M.A. Duncan, Int. Rev. Phys. Chem. 22 (2003) 407.
[3] J.M. Weber and H. Schneider, J. Chem. Phys. 120 (2004) 10056.
[4] A.D. Boese, H. Schneider, A.N. Gloess, and J.M. Weber, in preparation (2004).
[5] A. Sanchez, et al., J. Phys. Chem. A 103 (1999) 9573.
[6] L.D. Socaciu, et al., J. Am. Chem. Soc. 125 (2003) 10437.
[7] H. Schneider, A.D. Boese, and J.M. Weber, in preparation (2004).

Infrared Spectroscopy of XY - ·(C2H2)n Cluster Ions (XY = O2, C2H)
Holger Schneider, J. Mathias Weber *
Institut für Physikalische Chemie, Universität Karlsruhe, Kaiserstr. 12, 76229 Karlsruhe, Germany
* corresponding author; email: jmathias.weber@chemie.uni-karlsruhe.de
A - 13
Proton or hydrogen transfer is an important process in chemistry. The intermolecular
interaction potentials governing reactive processes can be studied by vibrational spectroscopy of
complexes containing the reactants.[1, 2] We report the infrared photodissociation spectra of
ion-acetylene clusters, with O2 - and C2H - as proton acceptors. The experimental results are
interpreted in the framework of density functional theory.
Complexes of strong ionic proton acceptors with acetylene molecules can be studied as models
for proton acceptors [3]. All studied complexes are formed by C2H2 molecules docking to the
ions by forming an H-bond. In the case of superoxide, each ligand binds to a lobe of the π*
orbital of O2 - , affording a similar binding motif for all acetylene molecules. In contrast, HC2 - has
only one ionic binding site, and the one of the ligands is favoured, while all others are less
strongly bound.
References
[1] W.H. Robertson and M.A. Johnson, Annu. Rev. Phys. Chem. 54 (2003) 173.
[2] M.A. Duncan, Int. Rev. Phys. Chem. 22 (2003) 407.
[3] P. Botschwina, et al., Faraday Discuss. 118 (2001) 433.
117

A - 14
118
Computational Study of (H2S) 2≤ n ≤ 10 Clusters
Mehmet Bahat and Ziya Kantarci
Gazi University, Physics Department, 06500, Teknikokullar, Ankara, Turkey.
Molecular clusters are the subject of continuing investigations both experimentally and
theoretically in recent years. One of them water clusters have been the subject of significant
research activity. However, little information for the H2S clusters is available from theoretical
and experimental point of view at present. Most calculations have focused on the dimer
structure. Experimentally photoionization studies for the H2S clusters through heptamer have
been studied.
We have studied structures,energies and vibrational spectra of (H2S) 2≤ n ≤ 6 clusters
computationally, will be send elsewhere.
In this study, we will present structure, energy, polarizability and hyperpolarizability properties
of (H2S) 2≤ n ≤ 10 clusters which calculated using B3LYP/cc-pVTZ level of theory.

Structural and spectral features of size selected water clusters in the
n=7-21 regime: Results from electronic structure calculations and
empirical potentials
A - 15
George S Fanourgakis 1 , Anita Lagutschenkov 2 , Gereon Niedner-Schatteburg 2 and Sotiris S. Xantheas 1
1 Chemical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, PO Box
999, MS K1-83, Richland, WA 99352, USA
2 Department of Chemistry, Chemie, University of Kaiserslautern, Erwin Schroedinger Strasse, 67663
Kaiserslautern, Germany
The structural patterns adopted by the clusters of the first few molecules of water are
determined from the maximization of hydrogen bonding, the minimization of dangling bonds
and the formation of local networks, which exhibit large cooperative effects. To this end, the
global minima of the first few water clusters are characterized by structures in which all
molecules are on the surface of the cluster. The structural transition between “all-surface” and
“internally solvated” water cluster structures is investigated using high-level ab-initio electronic
structure methods and the results are compared to the ones with empirical potentials. An
informative probing of these hydrogen bonding networks is achieved by infrared (IR)
spectroscopy in the 3000 – 4000 cm -1 range, a part of the spectra that corresponds to the
“fingerprint” of the underlying network and its connectivity. We present the spectral features
that are associated with the structural transition from “all-surface” to “internally solvated”
structures in water clusters. We furthermore rely on the use of Schlegel diagrams in order to
identify the most intense, red-shifted OH stretching vibrations which are used in order to probe
the underlying hydrogen bonding network.
119

Phase Transitions
121

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122

Structural changes in small and medium-size rare-gas cluster cations.
Aleš Vítek, František Karlický, and René Kalus
Department of Physics, University of Ostrava,30. dubna 22, 701 03 Ostrava, Czech Republic
A - 16
Constant-energy and constant-temperature Monte Carlo simulations have been performed to
localize temperature-dependent structural changes in selected krypton cluster cations, Kr3 + , Kr4 + ,
and Kr12-14 + . The trimer and tetramer cations are used to analyze possible structural changes in
the ionic cores of larger KrN + clusters, the Kr12-14 + cations are included as representatives of
these larger clusters to assess the role of solvation effects and to study the phase changes
occurring in neutral solvation shells. The intra-cluster interactions of KrN + are described by
means of previously developed models based on the diatomics-in-molecules approach with the
inclusion of the spin-orbit coupling and the most important three-body polarization interactions.
123

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124
Experimental study of the phase transformations
in molecular clusters of Ar and N2
O. G. Danylchenko, S. I. Kovalenko, V. N. Samovarov
B. Verkin Institute for Low Temperature Physics and Engineering, Natl. Academy of Sciences of Ukraine,
47 Lenin Ave., Kharkov, 61103, Ukraine
We use an electron diffraction technique to study the structure of substrate-free Ar and N2
clusters and nanoparticles formed in the process of homogeneous nucleation in a supersonic jet
isentropically expanding into vacuum. The average size N of aggregations varied between 5⋅10 2
and 1.5⋅10 5 atoms (molecules) per cluster. The temperature of clusters and nanoparticles was
T=(38±5) K in the diffraction zone.
Analysis of the obtained electron-diffraction patterns has shown for the first time the existence
of an amorphous phase in large rare-gas clusters (N≈600 atoms/cluster). As N increased in a
relatively narrow size interval a transition occurred from the amorphous phase to the multilayer
icosahedral one observed for N=1300 atoms/cluster. Formation of a crystalline face-centered
cubic (fcc) structure of argon with stacking faults took place for N=3⋅10 3 atoms/cluster which is
in good accordance with the previous observations [1,2]. The electron-diffraction patterns of
bigger clusters (N∼10 4 atoms/cluster) are shown to be characterized by hexagonal close-packed
(hcp) maxima along with the fcc peaks. The intensity of the hcp peaks grew with increasing
aggregation size, and for nanoparticles with N∼10 5 atoms/cluster we clearly detected (100),
(101), (103), and (202) peaks characteristic of an hcp structure with intensity comparable with
that of the fcc peaks.
In case of linear molecules like those of nitrogen, besides the central interaction between
particles there is a considerable contribution of non-central electrostatic forces which are
responsible for the orientational ordering of molecules at low temperatures. The structure of
such clusters can differ significantly from the structure of rare-gas clusters depending on the
anisotropic contribution to the total lattice energy. In contrast to amorphous argon clusters, for
nitrogen beams with N≈500 molecules/cluster we first observed the formation of aggregations
with multilayer icosahedral packing of molecules. The ‘wings’ of the most prominent
icosahedral-phase maximum (in the region corresponding to the (100) and (101) peaks of the
high-temperature β phase of N2, α-β phase transition in a bulk at T=35.6 K) are found to be
curved thus indicating the presence of traces of the β phase in these clusters. As the cluster size
grows at the same T in the diffraction zone, the diffraction pattern undergoes transformations
and for N∼10 3 molecules/cluster it contains maxima of both cubic (α) and hcp (β) phases.
Further cluster growing is accompanied by a decrease in the intensity of the cubic-phase peaks
and strenghening of the hcp peaks. Clusters with N∼10 4 actually have only the high-temperature
β phase.
We propose and discuss a mechanism underlying the observed structural transformations in Ar
and N2 which supposes cluster formation from a liquid droplet and takes into account the
kinetics of phase growth when there are energy barriers between phases.
References
[1] I. Farges, M.F. de Feraudy, B. Roult, G. Torchet, Adv. Chem. Phys. 70, 45 (1988).
[2] O.G. Danylchenko, S.I. Kovalenko, V.N. Samovarov, Low Temp. Phys. 30, 166 (2004).

Molecular Dynamics Simulations of the Melting-like Transition in
Homogeneous and Heterogeneous Alkali Clusters
Andrés Aguado and José M. López
A - 18
Department of Theoretical Physics, University of Valladolid, C/ Real de Burgos s/n, Valladolid, 47011,
Spain
A theoretical analysis of the equilibrium geometries and thermal behaviour of the impuritydoped
A1Na54 (with A=Li,K,Rb,Cs) clusters, of binary Li13Na42 and Na13Cs42 and of ternary
Li13Na32Cs12 nanoalloys is presented. The calculations are based on the orbital-free approach to
density functional theory and the classical newtonian equations to deal with the electronic and
ionic subsystems, respectively. The icosahedral symmetry of homogeneous Na55 is preserved in
the impurity-doped clusters, with the Li impurity located at the center of the icosahedron and
K,Rb and Cs impurities occupying a surface site. The ground state
isomer of Na13Cs42 and Li13Na32Cs12 nanoalloys is an onion-like polyicosahedral structure, with
a core shell formed by the element of highest surface tension and smallest atomic size, and a
surface shell formed by the atomic species of largest size and lowest surface tension. Li13Na42
adopts an amorphous-like structure, albeit with significant polyicosahedral local order, due to
partial mixing of Li and Na species in the core-shell. Regarding the thermal properties, the
impurity-doped clusters A1Na54 are found to melt in two well-defined steps upon heating, each
one associated to the activation of diffusive motion for atoms of a given species. Regarding the
thermal behavior of nanoalloys, we have not studied yet explicitly a representative number of
examples and can not draw very general conclusions. However, our partial results already
indicate that: (1) when the polyicosahedral ordering is not perfect and/or the structure is not
highly compact (as is the case for Li13Na42 and Na13Cs42), premelting effects are more relevant
than in corresponding homogeneous clusters; (2) if
polyicosahedral ordering is strictly preserved (as it
happens for Li13Na32Cs12) the relative stability of the
solid-like phase can be significantly enhanced. For
example, the surface of this ternary cluster (formed by
Cs atoms) melts at approximately 140 K, which is 50
K above typical surface melting temperatures of
homogeneous Cs clusters.
If possible, we will complement the results mentioned
in the previous paragraph with those of additional
molecular dynamics simulations on homogeneous and
heterogeneous alkali clusters which are still on the
way at the date of submission of this abstract.
References
Figure 1. Ground state structure of Li 13Na 30Cs 12.
[1] A. Aguado, L. E. González, and J. M. López, J. Phys. Chem. B 108, 11722 (2004).
[2] A. Aguado, J. M. López, and S. Núñez, Comp. Mat. Sci. to be published.
[3] A. Aguado and J. M. López, unpublished works.
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Phase Changes in Clusters: Targets for Experiments
R. Stephen Berry 1 , and Ana Proykova 2
1 Department of Chemistry and The James Franck Institute, The University of Chicago, Chicago,
Illinois 60637, USA
2 University of Sofia, Faculty of Physics, 5 James Bourchier Blvd, Sofia 1126, Bulgaria
It is now well established that some clusters exhibit the finite-system counterparts of firstorder
transitions, and that these differ from bulk phase transitions insofar as clusters may exist
in two or more phases in observable amounts, in thermal equilibrium. It is also apparent from
simulations that bulk second-order transitions may have small-system analogues that have either
one or two local free-energy minima, corresponding to second-order-like or first-order-like
behavior. These findings raise several questions that await experimental study. One is the
observation of sharp upper or (more likely) lower temperature bounds for the local stability of
the unfavored phase. A second is the possibility of observing and distinguishing between cases
in which phases persist long enough to exhibit well-defined, measurable characteristics and
cases in which the dynamic equilibrium between the phases is so labile that no well-defined
distinguishable phases can be observed. Still a third challenge is the possibility of observing
phase changes or phase coexistence that look first-order-like in small clusters but become
second-order in the large-system limit. With this challenge is the alternative of true secondorder-like
behavior in which multiple phases do not coexist because the free energy has only a
single minimum. All of these are experimental investigations that will almost certainly require
monodisperse cluster samples, because the phase behavior of small clusters is highly variable
and not at all monotonic with cluster size.

Rare Gases
127

A - 19
128

A - 20
Decay behaviour of dimer ions: kinetic energy distributions and 1/t law
J. Fedor 1 , K. Głuch 2 , S. Matt-Leubner 1 , O. Echt 3 , P. Scheier 1 , F. Hagelberg 4 , K. Hansen 5 , J. U. Andersen 6 ,
T. D. Märk 1
1 Institute for Ion Physics, Innsbruck University, Technikerstrasse 25, A-6020 Innsbruck, Austria
2 Institute of Mathematics, Physics and Informatics, Maria Curie-Skłodowska University, Lublin 20-031,
Poland
3 Dept. of Physics, University of New Hampshire, Durham, NH 03824, USA
4 Dept. of Physics, Atmospheric Sciences, and General Science, Jackson State University, Jackson, MS
39217, USA
5 Department of Physics, Gothenburg University, SE-41296 Gothenburg, Sweden
6 Institute of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus, Denmark.
There exists a plethora of data on metastable decay of large cluster ions. For instance, the
analysis of the kinetic energy distributions of fragment ions has led to the evaluation of their
binding energies [1] and the time dependence of the decay intensity has been shown to obey a
powerlaw [2]. These decays have been successfully described with statistical theories.
Dimers represent the system where the degree of randomization required for thermal statistical
treatment is not possible. Experimental findings on dimer ions however show that they can have
decay characteristics resembling those of the large clusters.
Here we present the measurements of the kinetic energy release distributions of the rare gas
dimer anions (Ne2 + , Ar2 + , Kr2 + , Xe2 + ) using a three sector field mass spectrometer, as well as the
measurements of decay intensity time dependence for the dissociation of the metal dimer anions
(Cu2 - , Ag2 - ) obtained on the ELISA storage ring in Aarhus. The decay behaviour has been
successfully explained either by the metastable electronic transitions in case of rare gases or by
the tunneling through the high angular momentum barrier in the metal anions. The quasicontinuum
of rotational states in the later case is sufficiently dense to lead to a 1/t law.
References
[1] K. Gluch, S. Matt-Leubner, O. Echt, R. Deng, J.U. Andersen, P. Scheier and T.D. Märk, Chem.
Phys. Lett. 385 449 (2004)
[2] K.Hansen, J.U.Andersen, P.Hvelplund, S.P.Møller, U.V.Pedersen and V.V.Petrunin,
Phys.Rev.Lett. 87 123401 (2001)
129

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130
Fragmentation dynamics of rare-gas trimer cations.
Ivan Janeček, Daniel Hrivňák, and René Kalus
Department of Physics, University of Ostrava,30. dubna 22, 701 03 Ostrava, Czech Republic
Hemiquantal, mean-field dynamics and recently developed extended diatomics-inmolecules
models of intra-cluster interactions with the inclusion of the spin-orbit coupling and
the most important three-body forces are used to study fragmentation of argon, krypton and
xenon trimer cations after a sudden ionization of respective vibrationally excited neutral trimers.
Both fragmentation from adiabatic and diabatic states is included and the computational results
are compared, where possible, with data from experiments as well as from other theoretical
studies. The main focus is on the role the spin-orbit coupling plays in the relaxation of the initial
electronic excitation and during its conversion into cluster vibrational energy. Kinetics of the
cluster fragmentation is thoroughly analyzed and recognized to consist of two (or even more)
consecutive first-order processes most probably involving the electronic relaxation and the
subsequent cluster decay.

High resolution electron ionization study of helium-clusters
S. Denifl 1 , S. Ptasińska 1 , F. Martinez 2 , K. Głuch 3 , S. Feil 1 , P. Scheier 1 , T. D. Märk 1
A - 22
1 Insitut für Ionenphysi,, Universität Innsbruck, Technikerstrasse 25, 6020 Innsbruck, Austria
2 Institut für Physik, Ernst Moritz Arndt Universität Greifswald, Domstrasse 10a,17487 Greifswald,
Germany
3 Institute of Physics, Maria Curie-Sklodowska University, Pl. Marii Curie-Sklodowskiej 1, 20-031 Lublin,
Poland
After many years of research the determination and interpretation of appearance energies
(AE’s) for clusters using electron impact ionization is still difficult and involves large error bars.
The reasons for this are a number of technical obstacles to prepare electrons with high-energy
resolution. In addition we are confronted with a complicated physical situation of a reaction
complex involving a quantum mechanical many body system. The use of photoionization
sometimes appears to be less difficult but nevertheless the AE values obtained are not directly
comparable to those obtained by electron impact studies. Both processes are intrinsically
different, because the transition complexes in the ionization process are not the same.
This work presents the high resolution study of the threshold behavior for small helium cluster
ions. The crossed electron/cluster beams apparatus used for these measurements consists of a
cluster source, a hemispherical electron monochromator and a quadrupole mass spectrometer. A
standard home-built hemispherical electron analyzer produces electrons with a typical energy
distribution of 150 meV. The helium clusters are produced by supersonic expansion in a cluster
source which can be cooled down to 8.5 K. Previously already all other rare gases (Ne, Ar, Kr,
Xe), H2-, D2-, N2- and N2O-clusters have been studied with the present experimental setup
(except a different cluster source was used). The data evaluation is basing on an extension of
Wannier’s law for the ionization of atoms towards the case of clusters. The present results for
helium cluster up to size n = 10 are compared with those of previous experiments with small
helium clusters using electron impact [1] or photon impact [2], respectively.
This work was supported by FWF, Wien, Austria, and the European Commission,
Brussels.
References
[1] R. Fröchtenicht, U. Henne, J. P. Toennis, A. Ding, M. Fieber-Erdmann, T. Drewello, J. Chem.
Phys. 104, 2548 (1996).
[2] B. E. Callicoat, K. Förde, L. F. Jung, T. Ruchti, K. C. Janda, J. Chem. Phys. 109, 10195 (1998).
131

A - 23
132
Surface Entropy of Argon Clusters
Mikael Kjellberg, Sergey Prasalovich, Vladimir Popok, Klavs Hansen, Eleanor E. B. Campbell
Department of Physics, Göteborg University, SE-41296 Göteborg, Sweden
The enhanced stability of certain cluster sizes is traditionally inferred from the enhanced
abundance of these species in mass spectra. For rare gas clusters, the stability pattern can be
described as due to a close packing of atoms into closed structures (shells) with the symmetry of
Mackay icosahedra. The mere presence of shell closings does not give any information on the
magnitude of the energies involved. A quantitative comparison requires knowledge of the
binding energies of the clusters. It is possible to extract this information from the mass spectra
by making reasonable general assumptions [1] with the restriction that only relative values can
be found. The flat abundance spectrum (after background subtraction) is related to relative
I ∝ D + C D − D G.
energies as ( )
N N+ 1 v N N+
1 /
This has been done in Fig 1(A) for masses around the N = 55 “magic number”. The amplitude
in the relative energy variations does not follow the same trend as the local abundance
variations. In particular the maximum in the relative energy is shifted to smaller N. The reason
for this is that the relative energies obtained in this procedure are not the dissociation energies,
DN, of the clusters but the free energies, FN = DN – TSN, where SN is identified with the surface
entropy (the natural logarithm of the number of ways the configurational ground state can be
contructed). This can be estimated from the structures calculated by Northby [2] and used to
extract the dissociation energies. This is shown in Fig. 1(B) and compared with the calculated
dissociation energies, where the absolute scale was obtained by scaling with the bulk and
surface energy. The agreement of the trend in the values is very satisfactory.
∆F (meV)
80
75
70
65
60
Figure 1. A, Left:Integrated peak intensities from Ar N + mass spectrum filled squares, (right y-axis) and the
dissociation energies extracted from the spectrum (free energies) (open squares, left y-axis). B, Right: Extracted
dissociation energies (free energies) (open circles), dissociation energies after subtraction of the entropy term (open
squares), calculated energies from Northby [2] (filled squares).
References
50 51 52 53 54 55 56 57 58 59 60
0
61
N
[1] K. Hansen and U. Näher, Phys. Rev. A , 60 1240 (1999).
[2] J.A. Northby, J. Xie, D.L. Freeman, J.D. Doll, Z. Phys. D 12 69 (1989)
∆F
I N
3
2
1
I N
Energies [meV]
85
80
75
70
65
60
55
50
45
∆F N,exp
D N,exp
D N,Northby
50 52 54 56 58 60
N

Photodissociation of rare-gas trimer cations.
Daniel Hrivňák 1 , René Kalus 1 , Florent X. Gadéa 2
1 Department of Physics, University of Ostrava, Czech Republic
2 Groupe NanoScience, CEMES, France
A - 24
Hemiquantal, mean-field dynamics and recently developed extended diatomics-inmolecules
models of intra-cluster interactions and electronic transitions in rare-gas cluster
cations are used to study the dissociation of argon, krypton and xenon trimer cations after
absorption of a photon. The main focus is on the importance of the spin-orbit coupling for the
photodissociation dynamics. The theoretical data on fragmentation channels, the kinetic energy
of photofragments and the ratios for the symmetric and asymmetric fragmentation are
thoroughly compared with the experimental data by Haberland’s group. A very good agreement
is obtained. The importance of initial vibrational excitations of the trimer cations is also
analyzed using a constant-temperature Monte Carlo sampling method. It has been found that the
kinetic energy of photofragments is only negligibly influenced by the initial heating of the
trimer, the ratios of the symmetric fragmentation change significantly with temperature
however, particularly in the temperature region corresponding to structural changes of the
trimers.
133

Semiconductors
135

A - 24
136

A - 25
Theoretical Investigation of the Influence of Ligands on Structural and
Electronic Properties of Indium Phosphide Clusters
Sudip Roy, Michael Springborg
Physikalische Chemie, Universität des Saarlandes, 66123 Saarbrücken, Germany
Results of a theoretical study of the effects of including ligands on stoichiometric InnPn
clusters are presented. We apply a parameterized density-functional method 1 and consider
clusters with n up to above 70. As ligands we consider H atoms and CH3 groups, and the results
are compared with our earlier ones for the naked clusters 2 . We find that the ligands lead to only
smaller structural changes, but that an enhanced In-to-P electron transfer in the outermost parts
of the clusters, that we observed for the naked clusters, is largely suppressed, so that there is a
more homogeneous In-to-P transfer throughout the whole cluster. Adding the ligands leads in
most cases to an increase in the HOMO-LUMO gap and, therefore, also to an increase in the
stability of the clusters. However, we find also that the HOMO-LUMO gap depends critically
on the type, sites, and number of the ligands that are added.
References
[1] G. Seifert, D. Porezag, and Th. Frauenheim, Int. J. Quant. Chem., 58, 185 (1996).
[2] S. Roy and M. Springborg, J. Phys. Chem. B , 107, 2771 (2003)
137

A - 26
138
Sizedependence of Electronic and Structural Properties of
Semiconductor Nanoparticles
Michael Springborg, Jan-Ole Joswig, Sudip Roy, Pranab Sarkar
Physical and Theoretical Chemistry, University of Saarland, 66123 Saarbrücken, Germany
Using a parameterized density-functional method we have calculated the electronic and
structural properties of naked AB semiconductor nanoparticles as a function of size with up to
around 200 atoms. We assumed that the structure is related to that of a spherical cutout of either
the zincblende or the wurtzite crystal structure, which subsequently is allowed to relax to its
closest total-energy minimum. In addition, we have also studied core/shell nanoparticles where
one semiconductor forms the shell on the core of another semiconductor. The properties that we
shall discuss include structure, optical gap, charge transfers and stability.

Structural, Electronic and Optical Properties of
Surface saturated Cadmium Sulfide Clusters
Johannes Frenzel 1 , Gotthard Seifert 1 , Jan-Ole Joswig 2 , Michael Springborg 2
1 Institut für Physikalische Chemie, Technische Universität Dresden, D-01062 Dresden, Germany
2 Institut für Physikalische Chemie, Universität des Saarlandes, D-66123 Saarbrücken, Germany
A - 27
Due to the quantum-confinement effects the optical properties of cadmium sulfide clusters
tune with respect to their size. In this theoretical work clusters up to 4 nm in diameter, derived
from the electronically almost degenerated crystal structures of cadmium sulfide, wurtzite and
zinc blende (sphalerite), were studied systematically using a simplified LCAO-DFT-LDA
method (DFTB) 1,2 . With a time-dependent extension (TD-DFRT-TB) 2 of this method the optical
spectra of bare and surface saturated cadmium sulfide clusters were calculated. Since there is a
strong dependency of the lowest unoccupied molecular orbitals on structural properties,
basically on the number single-bonded surface atoms the HOMO/LUMO gap trend to zero for
clusters having a large number of single bonded Cadmium atoms 3 . It is shown that effect,
caused by low lying cadmium 5s states, disappears when to these clusters surfactants are added,
namely hydrogen atoms and thiol-groups and their spectra show an asymptotical decreasing of
the HOMO/LUMO gap toward the bulk band gap of CdS while increasing their size.
Figure 1. Structurual shape (left side) and TD-DFRT-TB spectra (right side) of a spherical cadmium sulfide clusters,
unsaturated (dashed curve) and saturated (solid curve).The curves are broadened with Gausians (0.1 eV).
References
[1] Porezag, D. et al., Phys. Rev. B 51, 12947 (1995).
[2] Seifert, G. et al., Int. J. Quantum Chem. 58,185 (1996).
[3] Niehaus, T. et al., Phys. Rev. B 63, 085108 (2001).
[4] Joswig, J.-O. et al., J. Phys. Chem B 107, 2897 (2003).
139

Solvations
141

A - 27
142

Ionization Potentials of Large Sodium Doped Ammonia Clusters
Christof Steinbach, Udo Buck
Max-Planck-Institut für Strömungsforschung, Bunsenstrasse 10, 37073 Göttingen, Germany
A - 28
In a continuous neat supersonic expansion ammonia clusters are generated and doped with
sodium atoms in a pickup cell. In this way Na(NH3)n clusters are produced and photoionized by
a tunable dye laser system. The ions are mass analyzed in a reflectron time-of-flight mass
spectrometer, and the wavelength dependent ion signals serve for the determination of the
ionization potentials (IP) of the different clusters in the size range 10 < n < 500. For clusters n <
18 the results agree with those published previously. 1 In particular, the plateau for 10 < n

A - 29
Charge and Energy Transfer Processes Induced by Core Ionization of
Anion-Molecule Microsolvated Clusters
144
Nikolai V. Kryzhevoi, Lorenz S. Cederbaum
Theoretical Chemistry, Institute of Physical Chemistry, Heidelberg University,
Im Neuenheimer Feld 229, 69120 Heidelberg, Germany
Cluster physics pertains to exploration of various active topics of chemical science.
Solvation is among them. Studying microsolvated clusters provides an opportunity to gain
insight into the solvation phenomenon at the microscopic level. Anion-molecule microsolvated
clusters are of wide interest due to their unique properties. As well as being a subject of diverse
experimental studies, small clusters are also amenable to accurate theoretical treatments from
first principles. The first core level ab initio investigation of selected clusters of this type are
reported here. The localized character of core electrons allows one to probe local properties of
selected units of clusters providing information on the chemical state and interactions of each
unit with its local environment. Ionization of molecular core levels in anion-molecule clusters
induces, besides local excitations in the molecule itself, a variety of charge and energy transfer
processes which are nonlocal in nature. Low-lying satellites appearing in core level spectra due
to these nonlocal processes are apparently not present in spectra of free molecules and are a
peculiarity of clusters only. Energies and intensities of these satellites are found to strongly
depend on the chemical type of the anion as well as on the type of the ionized solvent molecule.
It is shown that valuable information on properties of anion-molecule clusters and their
monomers like the strength of anion-molecule interaction and the geometry of the clusters can
be obtain by studying charge and energy transfer satellites in core level spectra of clusters.

First principles studies on the reaction mechanisms for the intracluster
reactions in Mg + (H2O)n and Al + (H2O)n
Zhifeng Liu
Department of Chemistry
Chinese University of Hong Kong
Shatin, Hong Kong, China
A - 30
Size dependent reactions in solvation clusters provide invaluable clues to the link
between the microsolvation environment and the reaction mechanisms. The loss of a
hydrogen atom in an Mg + (H2O)n and the loss of a hydrogen molecule in an Al + (H2O)n
cluster are the classical examples of such reactions, which are turned on at a certain size
(5 for Mg + (H2O)n and 12 for Al + (H2O)n) and then turned off at a larger size (17 for
Mg + (H2O)n and 24 for Al + (H2O)n). The properties and structures of these clusters have
attracted much attention over the years. In this presentation, I will report the recent
progresses made in my group to understand the mechanisms for these size dependent
reactions by first principles calculations [1, 2, 3]. In the case of Al + (H2O)n, the reactivity
is actually due to its isomer (HAlOH) + (H2O)n-1 and is controlled by the cage-like cluster
structure, which is essential to bring a proton near the H--Al bond. In contrast, the
crucial factor in the case of Mg + (H2O)n is the solvation of the unpaired electron, as the
relative distance between the electron and the Mg 2+ center determines the barrier for the
production of the H atom. The details for both clusters provide interesting examples on
the subtle and intricate effects of solvation on chemical reactions.
References:
[1] C.K. Siu, Z.F. Liu, and J.S. Tse, “Ab Initio Studies on Al + (H2O)n, HAlOH + (H2O)n-1, and the Size
Dependent H2 Elimination Reaction”, J. Am. Chem. Soc. 124 (2002) 10846-60
[2] C.K. Siu, and Z.F. Liu, “Ab initio Studies on the Mechanism of the Size Dependent H Elimination
Reaction in Mg + (H2O)n”, Chem. Eu. J. 8 (2002) 3177-86
[3] C.K. Siu, and Z.F. Liu, “Reaction mechanisms for the size-dependent H loss in Mg + (H2O)n:
solvation controlled electron transfer”, submitted to Phys. Chem. Chem. Phys.
145

Surface
147

148

Alkali Metal Atoms and Clusters on Graphite:
a Density Functional Study
K. Rytkönen 1 , J. Akola 2 , M. Manninen 1
1 Nanoscience Center, P.O. Box 35, FIN-40014 University of Jyväskylä, Finland
2 Institut fϋr Festkörperforschung, Forschungszentrum Jϋlich, D-52425 Jϋlich, Germany
A - 31
Sodium atoms and clusters (≤ 5) on graphite (0001) are studied using density functional
theory, pseudopotentials and periodic boundary conditions [1]. A single Na atom is observed to
bind at a hollow site 2.45 Å above the surface with an adsorption energy of 0.51 eV. The small
diffusion barrier of 0.06 eV indicates a flat potential energy surface. Increased Na coverage
results in a weak adsorbate-substrate interaction, which is evident in the larger separation from
the surface in the cases of Na3, Na4, Na5, and the (2×2) Na overlayer. The binding is weak for
Na2, which has a full valence electron shell. The presence of substrate modifies the structures of
Na3, Na4, and Na5 significantly, and both Na4 and Na5 are distorted from planarity. The
calculated formation energies suggest that clustering of atoms is energetically favorable, and
that the open shell clusters (e.g. Na3 and Na5) can be more abundant on graphite than in the gas
phase. Analysis of the lateral charge density distributions of Na and Na3 shows a charge transfer
of ~0.5 electrons in both cases. Results for other alkali metals (Li, K, Rb, Cs) will be presented
too.
References
[1] K. Rytkönen, J. Akola, and M. Manninen, Phys. Rev. B 69, 205404 (2004).
149

A - 32
150
Single Atom Dispersion of Platinum on Carbon Nanotubes
Yong-Tae Kim 1 , Kazuyoshi Ohshima 1 , Koichi Higashimine 2 , Kazuo Kato 3 , Tomoya Uruga 3 , Keiichi
Osaka 3 , Kenichi Kato 3,4 , Masaki Takada 3,4 , Hiroyoshi Suematsu 3 , Tadaoki Mitani 1
1 School of Materials Science and Center for Nano Materials and Technology, Japan Advanced
2 Institute of Science and Technology (JAIST), 1-1 Asahidai, Tatsunokuchi, Ishikawa 923-1292, Japan
3 Japan Synchrotron Radiation Research Institute (JASRI)/SPring-8, 1-1-1 Kouto, Mikazuki,
Hyogo 679-5198, Japan
4 Core Research for Evolutional Science and Technology, Japan Science Technology Cooperation
(CREST/JST), 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
Electrocatalyst is the key factor to determine the performance of fuel cell. Generally, it is
prepared by the supporting electrocatalytical active material such as platinum on carbon
materials in order to elevate an activity and reduce the usage of novel metal. Carbon supports
therefore affect largely the properties of electrocatalyst such as dispersity, size distribution,
particle shape and intrinsic conductivity. Since the discovery of carbon nanotubes (CNT) in
1991 by Iijima 1 , the application to electrocatalyst supports has been attempted in order to utilize
their superior properties such as good intrinsic conductivity, adequate specific surface area,
accessible surface texture and electrochemical stability. However, there have been also a
limitation that it is difficult to disperse highly and uniformly electrocatalytical active material on
CNT, because they have the inert and plane surface which is difficult to wet in precursor
solution and easy to cause the agglomeration 2 . In order to solve this problem, we adopted the
introduction of thiol groups known to be the functional groups having a good affinity to novel
metal on CNT surfaces. It was expected that high dispersity could be obtained by preventing the
agglomeration among Pt clusters, since surface thiol groups formed the strong bonding with Pt
clusters.
Surprisingly, it was revealed that the surface of thiolated carbon nanotubes was covered with the
mono-layer of single platinum atoms bonded with the surface thiol groups over our expectation.
This phenomenon was confirmed with several analysis tools, such as X-ray Absorption Fine
Structure analysis (EXAFS, XANES), X-Ray Diffractometry (XRD) with synchrotron radiation
of SPring-8, X-ray Photoemission Spectrometry (XPS) and Transmission Electron Microscopy
(TEM).
Here we report the single atom dispersion as the extreme dispersed state of metal and the
possibility to control the cluster size uniformly from single atom.
References
O
Pt
S
NH
C
O
Pt
S
NH
C
Figure 1. Schematic diagram of single Pt atom dispersion on CNT.
[1] S. Iijima, Nature 354, 56 (1991).
[2] E. Dujardin, T. W. Ebbesen, H. Hiura, K. Tanigaki, Science 265, 1850 (1994).
O
Pt
S
NH
C
O
Pt
S
NH
C
O
Pt
S
NH
C

Self-Assembly of Metal Nanoclusters on Oxide Surfaces
N. Berdunov 1 , G. Mariotto 1 , S. Murphy 1 , K. Balakrishnan 1 , Y. M. Mukovskii 2 , I. V. Shvets 1
1 SFI Laboratories, Physics Dept., Trinity College Dublin, Ireland
2 MISIS, Leninsky Prospect 4, Moscow 119991, Russia
A - 33
The self-assembly of ordered arrays of metal nanoclusters is a fascinating scientific
phenomenon as well as a particularly promising subject for technological applications, such as
microelectronics, ultra-high density recording, corrosion and catalysis. For example, magnetite
and iron play an important role in industrial processes such as the production of hydrogen and
the synthesis of ammonia. The ability of controlling the size and arrangement of Fe
nanostructures may influence the way catalytic processes take place.
We have studied the formation of Fe nanostructures on the magnetite (111) surface of single
crystals and thin films. The Fe3O4(111) surface exhibits an hexagonal 42 Å superstructure, when
annealed in oxygen atmosphere [1]. We have shown that this highly regular pattern is useful as
a template for the self-assembly of nanostructures.
We have deposited Fe films of 0.2, 0.5, 1 and 2 Å thickness at room temperature by means of
electron beam evaporation. STM images prove that ordered nucleation of nanoclusters takes
place only on the patterned regions of the surface, while random nucleation takes place on the
unpatterned regions (see Fig. 1). These results have been reproduced in the case of a 0.5 Å Cr
film. The metal nanostructures are characterized by a very regular size distribution over a length
of several hundreds nanometers.
Our results demonstrate that the self-assembly of crystalline Fe and Cr nanostructures takes
place on the preferential nucleation sites provided by the nanopatterned Fe3O4(111) surface. We
suggest that ordered arrays of nanostructures could be grown on different oxides displaying
long-range surface reconstruction, as recently demonstrated by the growth of ordered Pd
clusters on Al2O3 [2].
Figure 1. 80 nm × 80 nm STM image of 0.5 Å Fe deposited onto the Fe3O4(111) surface. Self-assembly of Fe
nanostructures takes place only on the patterned areas of the crystal (terrace A), while Fe nucleates randomly onto the
unpatterned areas (terrace B).
References
[1] N. Berdunov, S. Murphy, G. Mariotto and I.V. Shvets, Phys. Rev. B 70, 085404 (2004).
[2] S. Degen, C. Becker and K. Wandelt, Faraday Discuss. 125, 343 (2004).
151

A - 34
152
Supported Gold Clusters and Cluster-Based Nanoparticles:
Characterization, Stability and Growth Studies by In Situ Grazing
Incidence Small Angle X-ray Scattering Technique
Stefan Vajda 1 , Jeffrey W. Elam 2 , Byeongdu Lee 3 , Michael J. Pellin 4 , Sönke Seifert 3 , George Y.
Tikhonov 1 and Nancy A. Tomczyk 1 , Randall E. Winans 1,3
1 Chemistry Division, 2 Energy Systems Division, 3 Experimental Facility Division, and 4 Materials Science
Division
Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 6043, USA
Supported clusters possess unique, strongly size-dependent properties. However, the
Achilles heal of supported particles remains their sintering at elevated temperatures or when
exposed to mixtures of reactive gases. In this paper, the issue of thermal stability and
agglomeration of atomic gold clusters and nanoparticles produced by cluster deposition on
oxide surfaces is addressed as a function of deposited cluster size, level of surface coverage,
temperature and time of heat treatment by synchrotron X-ray radiation at the Advanced Photon
Source.
The continuous beam of gold clusters was generated in a laser vaporization source. The Aun +
clusters were deflected into setup with an incorporated mass spectrometer for the pre-selection
of narrow cluster distributions in the size range Aun + , n=2,…10, with 1 to 5 dominant sizes. As
support, silica as well as Al2O3 and TiO2 films grown by atomic layer deposition on
SiO2/Si(111) were used. Coverages up to 45% of atomic monolayer equivalents were employed.
The temperature region of aggregation was determined by gradually heating up the samples and
recording 2-D X-ray scattering images during the heat treatment. The analysis of the data
provides information about the average size and shape of supported particles [1].
The size of the nanoparticles formed on the surface upon cluster deposition and their thermal
stability exhibited a very strong dependence on the initial size of the clusters, level of surface
coverage and material of the support. When applying surface coverages higher than 5% ML,
aggregation of the clusters into nanometer-size particles with narrow size distribution prevailed.
With decreasing coverage, the fraction of not-aggregated clusters significantly increased. Heat
treatment led to final particle sizes determined by initial cluster size, coverage and length of
treatment. The most striking results were observed when depositing 2.5 % ML of Au7-Au10
clusters on SiO2/Si(111): particles of one size, corresponding to Au20 were formed. Moreover,
these particles exhibited extraordinary and unexpected thermal stability as well, not undergoing
aggregation until 400 °C, when an onset of a slow agglomeration takes place [2]. Work on
supported clusters of single size and in reactive gas atmosphere is currently under progress.
This work and use of APS was supported by the U.S. Department of Energy, Office of Basic
Energy Sciences, Division of Chemical Sciences, Geosciences, and Biosciences under contract
number W-31-109-ENG-38.
References
[1] R. E. Winans, S. Vajda, B. Lee, S. J. Riley, S. Seifert, G.Y. Tikhonov, N. Tomczyk, J. Phys.
Chem. B, 108, 18105 (2004).
[2] S. Vajda, R. E. Winans, J.W. Elam, B. Lee, M.J. Pellin, S.J. Riley, S. Seifert, G.Y. Tikhonov and
N. A. Tomczyk, invited paper, submitted to ACS.

Oxidation of free and supported Pd clusters
Bernd Huber 1 , Michael Moseler 1,2
1 Freiburger Materialforschungszentrum , Stefan-Meier-Strasse 21, 79104 Freiburg, Germany
2 Fraunhofer Institut für Werkstoffmechanik, Wöhlerstrasse 11, 79108 Freiburg, Germany
A - 35
The adsorption sites of O2 on neutral PdN clusters (N=1-5) were studied using spin density
functional theory [1]. Only for Pd1O2 molecular adsorption is found to be favorable. For Pd2-5O2
dissociative adsorption with the oxygen sitting on Pd bridge sites is preferred. For N=4,5 the
cluster increases its spin state from triplet to a quintet state in comparision to the pure gas phase
Pd cluster. For molecular adsorption the O-O bond gets activated to a superoxolike state.
While for the gas phase clusters the adsorption-induced relaxation of the PdN cluster was small,
we see for the oxidation on MgO supported clusters the breaking of Pd-Pd bonds and the
formation of nano-oxides reflecting the ionic crystal structure of the MgO underlayer (Fig. 1).
Figure 1. The formation of Pd4 nano-oxides on a MgO underlayer. While the oxidized gas phase Pd 4 cluster (a)
remains in the same structure as the pure cluster, supported Pd 4O 2 deforms into a structure reflecting the ionic crystal
structure of the MgO underlayer (b + c).
References
[1] B. Huber, H. Häkkinen, U. Landman and M. Moseler, Comp. Mat. Sci. (accepted).
153

A - 36
The Size-Evolution of the Optical Properties of Supported Gold
Clusters and Nanocrystals Studied by Cavity Ringdown Spectroscopy:
From the Atom to the Bulk
154
J. M. Antonietti, M. Michalski, H. Jones, and U. Heiz
Institute of Surface Chemistry and Catalysis, Universität Ulm, 89069 Ulm, Germany
Measuring the size-dependent electronic structure of supported clusters near the Fermi level
is of critical importance in order to understand the catalytic activities of supported clusters or to
tune the optical properties of cluster assembled materials with the number of atoms. Up to now,
extensive studies on the electronic structure of size-selected, supported clusters are sparse,
because of the experimental challenges which must be overcome: preparation of monodispersed
samples, high sensitivity required for recording the signal arising from a highly dilute sample,
detection of the signal due to the clusters from the intense background signal arising from the
substrate.
In order to overcome these problems, a new experimental setup has been designed and built to
perfom Cavity Ringdown Spectroscopy (CRDS) in the visible spectral range on size-selected
clusters deposited on silica in UHV conditions. The clusters are produced in a laser vaporization
source, size-selected in the gas phase, and soft-landed onto the substrate.
In this work, the ability to prepare monodispersed cluster samples is demonstrated. The ultimate
sensitivity of the setup is such that absorption cross-sections of 0.02 Å 2 with cluster coverage
down to 0.05% of a monolayer (~1 10 12 clusters/cm 2 ) can be detected. The absorption spectra of
gold clusters, Aun (n = 1, 4, 8, and 20) deposited on silica are presented. Additionally, the
optical properties of self-organized gold nanocrystals with well-defined diameters (1 to 20 nm),
prepared by chemical means and deposited on silica have been measured. The spectrum of the
atom exhibits sharp peaks which are attributed to atoms attached at various defect sites on the
surface. A dramatic size-sensitivity of the absorption properties of clusters is observed.
However, Au8 shows features which are associated with nanocrystals, rather than small clusters.

A - 37
The Influence of Growth Kinetics on Island Morphology for Antimony
and Bismuth Diffusion and Aggregation on Graphite
Bernhard Kaiser 1 , Bert Stegemann 1 , Shelley Scott 2;3 , Simon Brown 2;3
1 Institute for Chemistry, Humboldt-University, Berlin, Germany
2 The MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
3 Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand
The morphology of antimony and bismuth islands has been studied with scanning electron
microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy
(AFM). Altering the deposition parameters (particle flux and coverage) shifts the balance
between thermodynamics and kinetics. For antimony islands, we observe that for low flux and
coverage the islands are compact, but undergo a transition to dendritic morphologies for higher
flux and coverage regimes, consistent with previous investigations [1]. The islands also become
flatter with increasing flux. For bismuth islands, we find a morphology transition from
hexagonal to six-pointed star with increasing kinetic influence. Also, the island height is
independent of flux, and vertical growth proceeds via an unusual striped layer growth.
Furthermore, for bismuth it is possible to grow nanorods with a well-defined diameter of only a
few nanometers and a length of several micrometers.
References
[1] B. Kaiser, B. Stegemann, H. Kaukel, K . Rademann, Surf. Sci. 496, L18 (2002)
155

A - 38
156
Transition From One- to Two-Dimensional Island Growth During
Molecular Beam Epitaxy: A Monte Carlo Study
S. P. Shrestha 1 and C. Y. Park 2
1 Department of Physics, Patan M. Campus, Patan Dhola, Nepal
2 Department of Physics, Sung Kyun Kwan University, Suwon 440-746, South Korea
We present the Monte Carlo results for submonolayer island growth during Molecular
Beam Epitaxy using irreversible nucleation and growth model. We have monitored island
morphology and island anisotropy parameter for different diffusional and sticking anisotropy
case. We find that in anisotropic sticking case, when diffusion is isotropic, increase in D/F leads
highly elongated islands where as when diffusion is anisotropic, only slight elongation of
islands are observed. In this case, for all values of D/F ratio, increase in DA is observed to cause
decrease in island elongation. Thus, when sticking is anisotropic, diffusional anisotropy
produces adverse effect on island elongation. When sticking is isotropic islands always show 2d
nature and when it is highly anisotropic the islands show 1d nature. At intermediate sticking
ratio, the D/F ratio results in transition of island morphology from 1d nature at low D/F ratio to
2d nature at high D/F ratio.

Spectroscopy of free clusters and clusters on surfaces
Chunrong Yin 1 , I. Barke 2 , D. Böcker 2 , Th. Irawan 2 , H. Hövel 2 , and B. v. Issendorff 1
1 Department of Physics, University of Freiburg, Stefan-Meier Str. 21, D-79104 Freiburg, Germany
2 University of Dortmund, Experimentelle Physik I, D-44221 Dortmund, Germany
A - 39
Understanding the evolution of physical properties from free clusters to clusters on surfaces
is a prerequisite for the use of clusters in technical applications. Photoelectron spectroscopy
(PES) is a powerful tool to study the electronic properties of free clusters in vacuum as well as
of supported clusters. Scanning tunneling spectroscopy (STS) is able to probe the electronic
structure of individual clusters. Up to now, however, for metal clusters on surfaces these three
techniques seemed to yield rather different results. A direct comparison of the results obtained
on free clusters as well as on the same clusters deposited on well defined surfaces will hopefully
clarify this situation, and yield definite informations about the electronic structure of the
cluster/surface system and the nature of charge transfer processes between the cluster and the
surface. Furthermore this comparison is expected to improve the fundamental understanding of
the results of tunneling spectroscopy on metal particles.
Currently, a new setup is being built which will allow the deposition of size selected clusters on
surfaces within an existing surface science apparatus. Scanning tunneling microscopy (STM)
and ultraviolet photoelectron spectroscopy (UPS) will be performed on the deposited clusters
and can be compared to the results of photoelectron spectroscopy obtained on the free clusters.
Preliminary experiments have already been done on noble metal islands produced by deposition
of metal atoms on rare gas films. First results show a dependence of the island Fermi edge
position on the thickness of the isolating rare gas layer. Further measurements are underway.
157

A - 40
158
Multiple Size-Selected Cluster Deposition:
Epitaxial Growth at Thermal Energies
Kristoffer Meinander, Kai Nordlund, and Juhani Keinonen
Accelerator Laboratory, P.O.Box 43, FIN-00014 University of Helsinki, Finland
It has been known for some time that when a small enough cluster lands on a singlecrystalline
substrate it will align completely epitaxially upon impact [1]. In a previous study,
using molecular dynamics simulations, it was noted that the upper size limit of Cu nanoclusters
that will align epitaxially with a smooth (100) Cu substrate upon deposition at thermal energies
is linearly dependent on temperature [2]. Deposition of clusters with sizes below the upper size
limit will initially result in the formation of epitaxial structures on the surface of the substrate,
however, as deposition continues clusters may impact on previously deposited clusters. The
result of this may be a change in the likelihood of epitaxial alignment, as the deposition no
longer takes place on a smooth surface, and hence a lowering in the upper size limit of clusters
that can be used in the deposition of thick epitaxial films.
Molecular dynamics simulations of multiple Cu cluster deposition were carried for different
cluster sizes, over a temperature range of 0-750 K, in order to investigate the effect of cluster on
cluster impacts to the upper size limit of epitaxial alignment. For each cluster size, several
clusters were deposited in sequence, with a 2 ns interval between each cluster, on the same
initially smooth, (100) Cu substrate. Through analysis of the degree of epitaxy between each
deposition event, the maximum number of deposited clusters resulting in an epitaxial structure,
for each specific cluster size, could be determined as a function of temperature.
It was found that there is a substantial decrease in the upper size limit for epitaxial alignment
when two clusters are deposited, as compared to that for the deposition of one cluster, for cases
where the second cluster impacts directly on top of the one previously deposited. As the amount
of deposited clusters increases, this decrease in the upper size limit is lowered, and ceases
approximately after the fifth or sixth cluster.
References
[1] M. Yeadon et al., J. Elect. Microsc. 48 (Suppl.S), 1075 (1999).
[2] K. Meinander, J. Frantz, K. Nordlund, and J. Keinonen, Thin Solid Films 45/1-2, 297-303 (2003).

C58 on HOPG
A. Böttcher, P. Weis, S. Jester, A. Bihlmeier, D. Löffler, M. M. Kappes
A - 41
Institut für Physikalische Chemie, Universität Karlsruhe, Fritz-Haber-Weg 4, 76131 Karlsruhe, Germany
The process of electron-impact induced fragmentation of C60 molecules has been exploited
as an intense source of C58 + ions. The ionic beam was directed toward a HOPG substrate by a
system of electrostatic lenses. A new solid material grows on the substrate as result of gentle
deposition of C58 + ions (kinetic energy < 0.1 eV/atom). Thermal desorption spectra of the films
created indicate that neither substrate-mediated decomposition nor dimerization of C58 occurs.
The activation energy for desorption of C58 molecules from the HOPG surface is about 1 eV
higher than found for C60 molecules on the same substrate. The apparent binding energy varies
with increasing adsorbate coverage from 2 to 2.2 eV. The morphology of the deposited films
has been investigated by means of AFM and STM. A fractal growth of 2D islands has been
found to be the dominating deposition channel. The growth kinetics depends on the impact
energy and surface temperature.
159

A - 42
160
A comparative simulation of Al interaction with Ge and Si
nanoclusters
Ol’ga Ananyina, Olexandr Yanovs’ky
SSEM Department, Zaporozhye State University, Zhukovsky Str. 66, Zaporozhye, 69063 Ukraine, e-mail:
ananyina@zsu.zp.ua.
Results of quantum-chemical calculations of Al-clusters (Al2, Al3, Al4) interaction with Si
and Ge(100) surfaces are represented in this work. Al adsorption on clean semiconductor
surfaces has an important technological significance as one of the ways of receiving metalsemiconductor
contacts. Our calculations were carried out with the help of semi-empirical
MNDO method (modified neglect of differential overlap) for Si33(Ge33) and Si67(Ge67) clusters,
which are modeling the clean ordered Si(100)-(2×4) and Ge(100)-(2×1) surfaces. Cluster
geometry and total energy, atom bonds orders, value of the electron density, atom orbital
populations and molecular localized orbitals were calculated. Simulation of possible structures,
formed by Al-clusters on Si(Ge) surfaces is the goal of this work, because forming of the certain
adsorbates structure defines further growth of Al film.
Two possible states of surface covered with Al2 clusters were received: the Al-Al “vertical” and
“lateral” dimer models. Electronic states of Si(Ge)-(100) surface for different dimer models are
compared.
Fig.1. A result of Al2 - and Al3 adsorption on Ge(100)-(2×1) surface: a) a part of a cluster modelling clean
Ge(100) surface with adsorbed Al2; “lateral” Al dimers forming; b) a part of a cluster modelling clean
Ge(100) surface with adsorbed Al2; “vertical” Al dimers forming; c) cluster Ge63 with adsorbed Al3.
Al3 adsorption on the semiconductors surfaces can be accompanied by the dissociation of Al3
cluster on the Al atoms, which saturates bonds of surface atoms of Si-Si (Ge-Ge) dimers. But
minimal total system energy corresponds to the state when Al3 cluster adsorbed on the surface
without dissociation. An increase in aluminum cluster size causes the increase of cluster
dissociation probability.
The influence of surface defects on the processes of “surface - cluster” interaction and the
possible reaction mechanisms at different coverage of such surfaces by dihydride and
monohydride chemisorption phases are discussed. Comparative analysis of results of simulation
for clusters of different size is carried out.

Characterization and Catalysis on a Well-defined Pt Cluster
in NaY Zeolite
Xiong Liu 1 , Rüdiger-A. Eichel 2 , Emil Roduner 1
1 Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55
D-70569 Stuttgart, Germany
2 Institute of Physical Chemistry III, Darmstadt University of Technology, Petersenstraße 20
D-64287 Darmstadt, Germany
A - 43
Size effects of metal clusters play an important role in heterogeneous catalysis since the
electronic properties, reactivity and selectivity of catalysts with a few atoms are strongly sizedependent.
Platinum clusters dispersed in zeolites or on porous oxide supports are highly active
catalysts for the oxidation of CO and residual hydrocarbons in automotive exhaust catalysis and
for hydrogenation in petrochemical reactions. It is found that the catalyst performance increases
with decreasing Pt cluster size. Usually, in supported metal catalysts the cluster size, shape and
morphology are not uniform, which make the evaluation of catalytic properties complicated.
Therefore, the preparation and characterization of homogeneous size clusters for understanding
catalytic elementary steps and realizing catalysis on well-defined clusters is very desirable.
Recently, we have demonstrated that under carefully controlled conditions it is possible to
observe a single, well-defined small Pt cluster in zeolites by EPR spectroscopy. A highly
symmetric cluster with 12 paramagnetic equivalent Pt atoms was characterized by continuous
wave and pulse EPR. ENDOR and HYSCORE experiments reveal the proton hyperfine
couplings of the adsorbed hydrogen on the surface. The observed species may be Pt13H12 n+ [1]
or Pt13H20 n+ (n = +1 or +3) cluster with an icosahedral structure.
Hydrogen or deuterium adsorbed on the Pt cluster exchanges and is desorbed and re-adsorbed
reversibly. The desorption energy amounts to 0.69 eV per atom, in good agreement with
theoretical values based on DFT calculations. Exposure to CO results in the decomposition of
the cluster and growth of new paramagnetic Pt-carbonyl clusters. Amazingly, reaction with O2
is rather slow. SQUID measurements reveal that there is a large fraction of EPR silent
paramagnetic and diamagnetic Pt species. They are partly in electron transfer equilibrium with
the observed cluster.
2600 2800 3000 3200
Magnetic Field (G)
6% Pt/NaY; reduction in H 2
then exchanged by D 2
6% Pt/NaY; reduction in H 2
Figure 1. EPR spectrum of 6% Pt/NaY recorded at 20 K, demonstrating reversible exchange of hydrogen isotopes.
References
[1] T. Schmauke, R-A. Eichel, A. Schweiger, E. Roduner; Phys. Chem. Chem. Phys. 5, 3076 (2003).
161

A - 44
DFT-Investigations of coalescence behaviour of Si4 and Si7 clusters on
surfaces
162
Wolfram Quester 1 , Dominik Fischer 1,2 and Peter Nielaba 1
1 Fachbereich Physik, Universität Konstanz, 78457 Konstanz
2 IBM Zürich Research Laboratory, Säumerstraße 4, 8803 Rüschlikon
Experimental results show that Si4 and Si7 clusters do not form islands of bulk Si on weakly
interacting surfaces (HOPG). We investigated the coalescence behaviour using Density
Functional Theory implemented in the CPMD code (www.cpmd.org).
We calculated potential energy curves of two approaching Si4 clusters on two reaction channels.
It could be shown that there exists a fusion barrier which is higher than room temperature.
These calculations will be extended to Si7 clusters. To get informations about the influence of
the substrate a calculation of a Si4 cluster on a gold surface was perfomed. This simulation
revealed that gold is not suited as substrate for depositing Si clusters.

A - 45
Morphologies Studies of Mass Selected Au Clusters on Rutile TiO2 as a
Function of Impact Energy and Surface Temperature
P. Convers, R. Vallotton, R. Monot, W. Harbich
Institut de Physique des Nanostructures,
Ecole polytechnique Fédérale de Lausanne (EPFL),
CH-1015 Lausanne
In 1989 Haruta and coworkers have shown that small gold particles (diameter < 4 nm) are
catalytically active [1]. Gold was found to be even more efficient for temperatures below 400°C
than Pt, usually used for CO oxydation [2, 3]. More recent studies by Heiz et al. (Mass selected
Aun deposited on MgO) and Anderson et al. (Mass selected Aun deposited on TiO2) report a
pronounced size dependence of the catalytic activity [4, 5]. However informations on the
morphology of the clusters is sparse. Wahlström et al. showed that atomic Au thermally
deposited on a surface of TiO2(110) form clusters that are stabilized by oxygen vacancies at the
surface [6]. The clusters are small enough for catalysis, however a temperature increase causes a
sintering of the clusters and probably decreases the catalytic efficiency.
To understand the clusters morphology as a function of temperature, we deposit mass-selected
gold clusters with defined kinetic energy on a TiO2(110). The morphology is then studied by
STM after different heating cycles up to 1000 K. We observe that large cluster sizes (n = 7) and
high deposition energy (up to 4500 eV ) stabilize gold on the surface. Figure 1 is a typical STM
image of a deposit of Au7 on TiO2 at 20 eV after a heating cycle at 800 K.
References
Figure 1. Au 7/TiO 2 at 20eV after annealing at 800K
[1] M. Haruta, N. Yamada, T. Kobayashi, and S. Iijima, Journal of Catalysis 115, 301 (1989).
[2] M. Haruta, Catalysis Today 36, 153 (1997).
[3] M. Valden, X. Lai, and D. W. Goodman, Science 281, 1647 (1998).
[4] A. Sanchez, S. Abbet, U. Heiz, W.-D. Schneider, H. Häkkinen, R. N. Barnett, and U. Landman, J.
Phys. Chem. A 103, 9573 (1999).
[5] S. Lee, C. Fan, T. Wu, and S. L. Anderson, J. Am. Chem. Soc. 126, 5682 (2004).
[6] E. Wahlstrom, N. Lopez, R. Schaub, P. Thostrup, A. Ronnau, C. Africh, E. Laegsgaard, J.
Norskov, and F. Besenbacher, Phys. Rev. Lett. 90, 026101 (2003).
163

A - 46
164
Mass-selected Nanocrystal Superlattices
J. T. Lau 1 , H.Weller 2 , T. Möller 1
1 Technische Universität Berlin, IAPF PN 3-1, Hardenbergstraße 36, D-10623 Berlin
2 Universität Hamburg, Institut für Physikalische Chemie, Grindelallee 117, D-20146 Hamburg
Nanocrystal superlattices built of identical particles are expected to exhibit novel electronic and
optical properties that can be tuned by particle size and interparticle distance. Below a distance
of approx. 2–5 Å, for example, coherent tunneling coupling or exchange coupling between
nanocrystals is expected because of wave function overlap.
We will present the design of our experiment and discuss how superlattice properties can be
probed by X-ray absorption, X-ray photoelectron spectroscopy, X-ray scattering and
photoluminescence spectroscopy.

165

Author Index
167

168

Abbet, S.......................................................... 53
Aguado, A. ................................................... 125
Ahmed, M....................................................... 65
Akola, J......................................................... 149
Alamanova, D............................................... 105
Alexandrova, A. N........................................ 112
Ananyina, O. ................................................ 160
Andersen, J. U. ............................................. 129
Anderson, S. L.................................................. 7
Andersson, M. ................................................ 50
Antonietti, J. M....................................... 53, 154
Arredondo, M. G. ........................................... 49
Asmis, K. R. ............................................. 55, 59
Bahat, M....................................................... 118
Balaj, O. P. ..................................................... 25
Balakrishnan, K............................................ 151
Balbás, L. C.................................................... 57
Balteanu, I. ..................................................... 25
Barat, M.......................................................... 13
Barke, I......................................................... 157
Barnakov, Y. A................................................. 9
Bartels, Chr..................................................... 69
Baruah, S. ....................................................... 96
Bechthold, P. S. .............................................. 51
Belosludov, R. V. ............................................. 9
Benz, L. .......................................................... 16
Berdunov, N. ................................................ 151
Berry, R. St................................................... 126
Bertram, N................................................ 88, 89
Beuhler, R. J. .................................................. 54
Beyer, M. K.................................................... 25
Bihlmeier, A. ................................................ 159
Blaum, K. ....................................................... 96
Block, M......................................................... 96
Blom, M. N................................................... 106
Böcker, D. .................................................... 157
Boese, A. D. ................................................. 116
Boldyrev, A. I............................................... 112
Bolton, K. ....................................................... 41
Bonačić-Koutecký, V. ........................ 11, 62, 75
Bondybey, V. E. ............................................. 25
Böttcher, A. .................................................. 159
Bousquet, G.................................................... 73
Bouteiller, Y. .................................................. 12
Bowen, Jr., K. H............................................... 6
Bowers, M. T.................................................. 16
Bréchignac, C. .................................................. 3
Brown, S....................................................... 155
Brück, J........................................................... 47
Brümmer, M. .................................................. 59
Buck, U................................................... 29, 143
Bulusu, S. ..................................................... 112
Buratto, S. K................................................... 16
Bürgel, Chr..................................................... 62
Burmeister, F.................................................. 66
Campbell, E. E. B............................. 40, 68, 132
Castleman Jr., A. W.................................. 26, 62
Cederbaum, L. S........................................... 144
Chaudhuri, A...................................................96
Chelikowsky, J. R. ..........................................22
Cheshnovsky, O. .............................................93
Chrétien, St. ....................................................16
Christen, W. ..................................................115
Claas, P. ..........................................................72
Concina, B. .....................................................38
Convers, P.....................................................163
Cordes, J. ........................................................89
Danylchenko, O. G. ......................................124
de Heer, W.......................................................19
Dedonder-Lardeux, C. ....................................13
Denifl, S..................................................38, 131
Desfrançois, C...........................................12, 13
Dietsche, R......................................................88
Ding, F. ...........................................................41
Dinh, M...........................................................73
Dmitruk, I....................................................9, 85
Dong, Y...........................................................48
Donges, J.........................................................32
Döppner, T......................................................71
Droppelmann, G..............................................72
Duncan, M. A....................................................5
Eberhardt, W.............................................51, 66
Echt, O. ...................................................38, 129
Ehrler, O. T. ....................................................39
Eichel, R.-A. .................................................161
Elam, J. W.....................................................152
Engelke, M......................................................74
Fan, Ch..............................................................7
Fanourgakis, G. S..........................................119
Fayeton, J. A. ..................................................13
Fedor, J. ........................................................129
Fehrer, F..........................................................73
Feil, S......................................................38, 131
Fennel, Th. ......................................................71
Fernández, E. M..............................................57
Fielicke, A...............................................45, 103
Fischer, D......................................................162
Fischer, T. .......................................................88
Fontanella, S. ..................................................59
Frenzel, J.......................................................139
Furche, F. ........................................................39
Gadéa, F. X. ..................................................133
Galak, M. ........................................................85
Ganteför, G. ..................................61, 74, 88, 89
Gemming, S. ...................................................30
Giniger, R........................................................93
Glaser, L. ........................................................17
Głuch, K..........................................38, 129, 131
Grégoire, G. ..............................................12, 13
Grigoryan, V. G. ...........................................105
Gromov, A. .....................................................40
Haberland, H...................................................32
Hagelberg, F..................................................129
Häkkinen, H................................46, 87, 97, 104
Hammer, B......................................................56
Hampe, O........................................................52
169

Hansen, K................................. 40, 68, 129, 132
Harbich, W. .................................................. 163
Hedén, M.................................................. 40, 68
Heiz, U. .................................................. 53, 154
Herfurth, F...................................................... 96
Herlert, A.......................................... 96, 98, 110
Higashimine, K............................................. 150
Hippler, T. ...................................................... 32
Hock, Chr. ...................................................... 69
Horoi, M......................................................... 28
Hövel, H. ...................................................... 157
Hrivňák, D............................................ 130, 133
Huang, X. ....................................................... 22
Huber, B. .............................................. 111, 153
Ikeda, K. S...................................................... 76
Irawan, Th. ................................................... 157
Jackson, K. A. .......................................... 28, 80
Janeček, I...................................................... 130
Janssens, E.................................................... 108
Jena, P............................................................. 23
Jester, S......................................................... 159
Jeyadevan, V. ................................................... 9
Johansson, M. P.............................................. 42
Jones, H. ....................................................... 154
Jonsson, F....................................................... 40
Joswig, J.-O. ......................................... 138, 139
Jouvet, C......................................................... 13
Judai, K........................................................... 53
Jusélius, J........................................................ 42
Kaiser, B....................................................... 155
Kalus, R........................................ 123, 130, 133
Kang, H. ......................................................... 13
Kantarci, Z.................................................... 118
Kappes, M. M........................... 39, 52, 106, 159
Karlický, F.................................................... 123
Kasuya, A................................................... 9, 85
Kato, K. ........................................................ 150
Kawazoe, Y. ..................................................... 9
Kaya, K........................................................... 31
Keinonen, J................................................... 158
Kellerbauer, A. ............................................... 96
Kemper, P....................................................... 16
Kern, K........................................................... 15
Khan, F. A. ..................................................... 49
Khanna, S. N. ................................................. 86
Kim, J. H. ....................................................... 65
Kim, Y. D..................................... 61, 74, 88, 89
Kim, Y.-T. .................................................... 150
Kimble, M. L.................................................. 62
Kiran, B. ........................................... 58, 60, 112
Kjellberg, M. ................................................ 132
Klingeler, R. ................................................... 51
Kluge, H.-J. .................................................... 96
Knickelbein, M. B. ......................................... 20
Kobayashi, T. ................................................. 76
Kolmakov, A. ................................................. 16
Kondow, T...................................................... 21
Kordel, M. .................................................... 106
Koskinen, P. ................................................. 104
170
Kostko, O................................................32, 109
Kovalenko, S. I. ............................................124
Krause, T.......................................................115
Kresin, V. V............................................67, 107
Kresin, V. Z. ...................................................67
Kronik, L.........................................................22
Kryzhevoi, N. V............................................144
Kudo, T. ............................................................9
Kuhnen, R. ......................................................69
Kumar, V. .........................................................9
kyun Lee, E.....................................................37
Lagutschenkov, A. ..................................47, 119
Landman, U. ...................................................53
Lassesson, A. ................................................110
Lau, J. T. .......................................................164
Leavitt, A. J.....................................................49
Lecomte, F. .....................................................12
Lee, B............................................................152
Lee, S. ...............................................................7
Li, J. ........................................................58, 112
Li, X..........................................................58, 60
Lievens, P................................................50, 108
Lifshitz, C. ......................................................38
Lightstone, J....................................................54
Lim, D. C. .................................................61, 88
Liu, X............................................................161
Liu, Z. .......................................................9, 145
Löffler, D. .....................................................159
López, J. M. ..................................................125
Lopez-Salido, I..........................................61, 88
Lucas, B. .........................................................12
Lüttgens, G......................................................51
Makmal, A. .....................................................22
Malakzadeh, A. ...............................................69
Mamykin, S. V..................................................9
Manninen, M.................................................149
Mariotto, G....................................................151
Märk, T. D. .....................................38, 129, 131
Martinez, F......................................98, 110, 131
Martins, M. .....................................................17
Marx, G.............................................96, 98, 110
Matt-Leubner, S. .....................................38, 129
Meijer, G...........................................45, 59, 103
Meinander, K. ...............................................158
Meiwes-Broer, K.-H. ................................70, 71
Metiu, H..........................................................16
Michalski, M.................................................154
Milczarek, G. ....................................................9
Mitani, T. ......................................................150
Mitrić, R....................................................62, 75
Mitsui, M. .......................................................31
Molina, L. M...................................................56
Möller, T. ......................................................164
Monot, R. ......................................................163
Moore, N. A....................................................62
Moro, R.........................................................107
Moseler, M....................................104, 111, 153
Mukherjee, M..................................................96
Mukovskii, Y. M...........................................151

Murakami, J.................................................... 24
Murphy, S..................................................... 151
Nakajima, A. ............................................ 31, 79
Neeb, M.................................................... 51, 66
Neukermans, S.............................................. 108
Neumaier, M................................................... 52
Neumark, D. M......................................... 10, 65
Niedner-Schatteburg, G.................... 47, 81, 119
Nielaba, P. .................................................... 162
Niemietz, M.................................................... 74
Nirasawa, T. ..................................................... 9
Nordlund, K.................................................. 158
Ohshima, K................................................... 150
Ohsuna, T. ........................................................ 9
Ohta, T............................................................ 21
Osaka, K....................................................... 150
Ovchinnikov, Y. N. ........................................ 67
Palmer, R. E. .................................................. 14
Pankewitz, T................................................... 47
Park, C. Y..................................................... 156
Park, J............................................................. 37
Parks, J. H................................................. 8, 106
Patterson, M. .................................................. 54
Pedersen, D. B................................................ 45
Pellin, M. J. .................................................. 152
Peterka, D. S................................................... 65
Pfeffer, B. ....................................................... 47
Pontius, N....................................................... 51
Popok, V....................................................... 132
Prasalovich, S. .............................................. 132
Proykova, A.................................................. 126
Przystawik, A. ................................................ 70
Ptasińska, S............................................. 38, 131
Quester, W.................................................... 162
Rabinovitch, R.............................................. 107
Radcliffe, P..................................................... 70
Ratsch, Chr................................................... 103
Rayner, D. M.................................................. 45
Reif, M. .......................................................... 17
Reinhard, P.-G................................................ 73
Ritter, H.......................................................... 98
Roduner, E.................................................... 161
Romanyuk, V. ............................................ 9, 85
Ronen, S. ........................................................ 93
Rönnow, E...................................................... 40
Rosén, A......................................................... 41
Roßteuscher, T................................................ 25
Röttgen, M. A................................................. 53
Roy, S................................................... 137, 138
Rytkönen, K. ................................................ 149
Samovarov, V. N.......................................... 124
Santambrogio, G............................................. 59
Santa-Nokki, T. .............................................. 46
Sarfraz, A. .................................................... 115
Sarkar, P. ...................................................... 138
Sauer, J. .......................................................... 59
Sawada, S. ...................................................... 76
Scheier, P........................................ 38, 129, 131
Schermann, J.-P........................................ 12, 13
Schmidt, M......................................................32
Schneider, H..........................................116, 117
Schooss, D. ...................................................106
Schulz, C.-P. ...................................................72
Schweikhard, L. ................................96, 98, 110
Scott, S..........................................................155
Seifert, G.........................................30, 104, 139
Seifert, S. ......................................................152
Serrano, D. ......................................................49
Shim, J. ...........................................................37
Shimizu, Y. .....................................................76
Shinoda, K. .......................................................9
Shrestha, S. P. ...............................................156
Shvets, I. V....................................................151
Silverans, R. E. .............................................108
Simard, B. .......................................................45
Sivamohan, R....................................................9
Springborg, M................. 48, 105, 137, 138, 139
Srinivas, S. ......................................................80
Stairs, J..........................................................106
Stanzel, J. ........................................................66
Stegemann, B................................................155
Steinbach, Chr.........................................29, 143
Stienkemeier, F. ..............................................72
Suematsu, H..................................................150
Sun, Q. ............................................................23
Sundararajan, V. ...............................................9
Sundholm, D. ..................................................42
Suraud, E.........................................................73
Swenson, D. R. ...............................................94
Takada, M. ....................................................150
Terasaki, A......................................................21
Terasaki, O........................................................9
Tiggesbäumker, J. .....................................70, 71
Tikhonov, G. Y. ............................................152
Tohji, K.............................................................9
Tomczyk, N. A..............................................152
Tong, X. ..........................................................16
Tono, K. ..........................................................21
Torres, M. B....................................................57
Uruga, T........................................................150
Vaara, J. ..........................................................42
Vajda, St. ......................................................152
Vallotton, R...................................................163
Veldeman, N. ..........................................50, 108
Velegrakis, M..................................................99
Vetter, M.........................................................47
Vítek, A.........................................................123
von Gynz-Rekowski, F. ..................................88
von Helden, G.........................................45, 103
von Issendorff, B............... 32, 69, 109, 111, 157
Wallace, W. T. ................................................49
Walsh, N. ......................................................110
Walter, L. ......................................................106
Walter, M........................................................97
Wang, C. .........................................................65
Wang, L.-S........................................58, 60, 112
Wang, Q..........................................................23
Wang, X........................................................108
171

Weber, J. M. ................................... 39, 116, 117
Weigend, F. .................................................... 52
Weis, P. ........................................................ 159
Weller, H. ..................................................... 164
Whetten, R. L. ................................................ 49
White, M. G.................................................... 54
Wies, St. ......................................................... 47
Winans, R. E................................................. 152
Wolf, I. ........................................................... 93
Wörz, A. S...................................................... 53
Wöste, L. .................................................... 4, 59
Wu, T................................................................ 7
Wurth, W.................................................. 17, 81
172
Wyrwas, R. B..................................................49
Xantheas, S. S. ..............................................119
Xia, C............................................................107
Yamaguchi, W. ...............................................24
Yanovs’ky, O................................................160
Yazidjian, Ch. .................................................96
Yeschenko, O..................................................85
Yin, Ch..........................................................157
Yoon, B...........................................................53
Zeng, X. Ch...................................................112
Zhai, H. J...........................................58, 60, 112
Zhang, H.-F.....................................................58

Time
8.30 a.m.
9.15 a.m.
10.00 a.m.
10.30 a.m.
11.15 a.m.
12.00 p.m.
2.00 p.m.
-
4.00 p.m.
5.00 p.m.
5.45 p.m.
Sunday Monday
Tuesday Wednesday Thursday Friday
28 February 05
27 February 05
8:20 Opening
1 March 05 2 March 05 3 March 05 4 March 05
Arrival
C. Bréchignac
Metal Clusters and Oxygen
L. Wöste
Reactivity Ag+Au Clusters
M. A. Duncan
IR of Metal Complexes
K. H. Bowen, Jr.
Diffuse Electron States
S. L. Anderson
Model Au Catalysts
J. H. Parks
Structural Order in Metal Clusters
D. M. Neumark
Dynamics and Droplets
V. Bonačić-Koutecký
Tailoring functionality by size
C. Desfrancois
New Infrared Spectroscopy Tech.
C. Jouvet
The H-Transfer Reaction
R. E. Palmer
Immobilisation of Proteins
K. Kern
Architecture at surfaces
W. A. de Heer
Cluster Ferroelectricity
M. B. Knickelbein
Molecular Magnets
A. W. Castleman, Jr.
Cluster Assembled Materials
M. F. Jarrold
Al/Ga Cluster Melting
HT 3 HT 8
HT 5 HT 10
HT 7
K. Kaya
Soft-Nano-Molecular Clusters
H. Haberland
Melting and Magic Numbers
6.30 p.m. A. Kasuya (CdSe) n Clusters S. K. Buratto Ag n+Au n on TiO Concluding Remarks (P. Jena)
*) Please see Table of Contents for the Poster Sessions
Schedule
Fermion/Boson Clusters+Catalysis
Coffee
Lunch
Discussions
K. Tono Oxidation of Cr n/Mn n
L. Kronik Mag. Semiconductors
Q. Sun Nanobullet for Tumor
J. Murakami N 2 on supported W n
M. Beyer CO-Oxidation on Pt n
Special P. Leiderer Talk 15
Potentials+Prospects of Nanoscience
M. Horoi Phase Transitons
U. Buck Na-doped H 2O Clusters
G. Seifert MoS Clusters
7.00 p.m.
Dinner Conference
8.30 p.m.
Poster
M. Martins Magnetic Clusters
Poster
Dinner
9.15 p.m.
Session A *)
U. Landman
Session B *)
Post Conference Session
Sketch: Scientific Dialogology - four
techniques for asking proper questions
Departure after
breakfast