Book of Abstracts Book of Abstracts - Universität Konstanz

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).
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