Eighth Condensed Phase and Interfacial Molecular Science (CPIMS)

Generation, Detection and Characterization of Gas-Phase Transition Metal
Containing Molecules (DE-FG02-04ER15603)
Timothy C. Steimle
Department of Chemistry and Biochemistry
Arizona State University
Tempe, Arizona 85287-1604
E-mail: tsteimle@asu.edu
I. Program Scope
Gas-phase transition metal containing molecules serve as ideal venues for testing
computational methodologies being developed to predict chemical properties of more extended
metal-containing catalysis because the properties of these simple molecules can be precisely derived
from high-resolution spectroscopic measurements. The focus of this project is to determine
geometric and electronic structure for both ground and low-lying excited states of these molecules
from the analysis of high resolution electronic spectra. The determined properties include electronic
state energies, bond lengths and angles, vibrational frequencies, permanent electric dipole moments,
�el � , magnetic dipole moments, �m � , magnetic hyperfine interactions and radiative lifetimes. The
�el � and �m � values are derived from the analysis of the spectral shifts and splittings induced by the
application of either an external static electric (i.e. Stark effect) or magnetic (i.e. Zeeman effect)
field. �el � gives insight into the polarity of the chemical bonds and �m � into the number of unpaired
electrons. A knowledge of �el � and �m � is essential for developing schemes for kinetic energy
manipulation (i.e. trapping) and enters into the description of numerous physical phenomena. The
spatial distribution and nature of the chemically relevant valence electrons is garnered from analysis
of the magnetic hyperfine interactions. The established synergism between experiments and theory
for these simple molecules guides computations, particularly those based on density functional
theory, for more extended chemical systems (e.g. clusters, nanoparticles and surfaces).
II. Recent progress
A. Platinum containing molecules: PtF and PtC
1. Microwave study of PtC (Publ.#9)
A high-level ab initio calculation performed by Minaev et al [PCCP 2(2000) 2851] suggested
1 �
that our previously assigned A"
� (Te � 13,200 cm -1 1 ) and A' � (Te � 12,643 cm -1 ) states of PtC
were actually the �= 0 + and 1 components of a 3 � state. Here we have used the analysis of the
elec
1
nuclear spin-rotation interaction parameter, C , for the X I
�
� state to probe the electronic state
elec
distribution. C is given by 2 I
nd order perturbation theory as:
1 � 2
a ˆL
0n
X �
elec
x n
CI= 4B�
. (1)
E � E
n n
In Eq. 1
� �0
�
�3
a0 n = � �2g I �N�B��0 r n
4�
h
�
with r being the position of the valence electrons relative
� �
to the nuclei with non-zero spin, Lˆ is the component of the total electronic orbital angular
x
momentum operator. It is evident form Eq. 1 that the location and nature of electronic states, n ,
1
relative to the X �
elec
� state can be derived from an analysis of the C . A molecular beam
I
pump/probe microwave optical double resonance (PPMODR) technique was used to record the
pure-rotational spectrum of the 194 Pt 12 C, 195 Pt 12 C and 196 Pt 12 C isotopologues (Figure 1).
The determined C (= 138(12) kHz) supports the re-assignment.
eff
I
171
0