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"Ultrafast Excited State Proton Transfer: Reactive Dynamics by Multidimensional Wavepacket
Motion" S. Lochbrunner, K. Stock, V. de Waele, and E. RiedleFemtochemistry and Femtobiology: Ultrafast Dynamics in Molecular Science, A. Douhal and J. Santamaria, eds. (World Scientific Publishing House, 2002), 202 - 212 Abstract: The ultrafast excited state intramolecular proton transfer was investigated in a number of molecules with identical and differing heteroatoms in the H-chelate ring. Time resolved absorption measurements with 30 fs resolution were performed with a fully tunable UV-visible pump probe spectrometer. A very similar behavior of all systems is found. The strongly Stokes shifted product emission is delayed by a small but finite amount and all signals display strong oscillatory contributions. The step like emission rise indicates that the reactive process proceeds as a ballistic wavepacket motion from the Franck-Condon region to the product well. The delay in the order of 50 fs results from the inertia of the participating nuclei and not from rate determining coupling matrix elements. The signal oscillations are due to ringing in a finite number of product normal modes that are displaced by the proton transfer reaction. From the detailed analysis of the periodic wavepacket motion a clear microscopic picture of the initial dynamics and the molecular deformations is reconstructed. BMO authors (in alphabetic order): Vincent de Waele Stefan Lochbrunner Eberhard Riedle Kai Stock Order Hardcopy |