Berlin 2001 – scientific programme
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MO: Molekülphysik
MO 1: Posters Monday: Clusters, Fullerenes and Nanotubes
MO 1.18: Poster
Monday, April 2, 2001, 12:30–15:00, AT3
Feedback Optimal Control of Wavepacket Dynamics in Small Mixed Alkali Clusters — •Andreas Bartelt1, Shinishirou Minemoto2, Cosmin Lupulescu1, Stefan Vajda1, and Ludger Wöste1 — 1Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin — 2School of Science, The university of Tokyo, 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033, Japan
The results of an adaptive feedback optimization experiment on mixed alkali metal clusters will be presented. The cluster beam is produced by coexpansion of alkali metal vapor with argon carrier gas into the vacuum. The emerging clusters are ionized by taylored femtosecond laser pulses. Pulse shaping is performed by spectral filtering with a programmable double mask liquid crystal modulator. The spectral phase and amplitude of the pulses are optimized by a selflearning algorithm based on Evolutionary Strategies. Optimization is achieved by using the ion signal as a feedback in order to iteratively maximize the ion yield.
The robustness of the experiment will be demonstrated on molecular systems exhibiting wavepacket oscillation in their excited states: the predissociating Na2K and its dominant fragment NaK. The highest yield of NaK+ and Na2K+ were produced by pulse trains consisting of three pulses. The time shift between the pulses is correlated to the wavepacket propagation in the excited state. The results agree well with the oscillation times of the transient pump-probe spectra [1].
[1] S. Vajda, S. Rutz, J. Heufelder, P. Rosendo, H. Ruppe, P. Wetzel, and L. Wöste, J. Phys. Chem. A 102, 4066 (1998)