Berlin 2001 – scientific programme

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MO: Molekülphysik

MO 1: Posters Monday: Clusters, Fullerenes and Nanotubes

MO 1.11: Poster

Monday, April 2, 2001, 12:30–15:00, AT3

Time-resolved studies of energy transfer from a vibrationally excited I₂⁻ chromophore into surrounding Ar or CO₂ clusters — •Roland Wester, Alison V. Davis, Arthur E. Bragg, and Daniel M. Neumark — Department of Chemistry, University of California, Berkeley CA, 94720, USA

The energy loss from vibrationally excited I₂⁻ anions into a solvent network has been studied for size-selected I₂⁻(Ar)_n and I₂⁻(CO₂)_n clusters. Using femtosecond stimulated emission pumping (SEP), vibrational wavepackets have been created at different excitation energies in the ground electronic state of the I₂⁻ chromophore. The coherent oscillations of these wavepackets, their dephasing and the continuous energy loss into the cluster have been investigated using femtosecond photoelectron spectroscopy (FPES). The energy loss manifests itself in both the increase in oscillation frequency while the wavepacket moves down in the I₂⁻ potential well and in a shift of the photoelectron spectra towards smaller kinetic energies. Subsequent evaporation of CO₂ molecules due to the transferred energy has also been probed by measuring photofragment mass distributions in a reflectron TOF spectrometer. From the number of evaporated CO₂ molecules at different excitation energies the average CO₂ binding energy can be estimated.