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MO: Molekülphysik

MO 2: Femtosekundenspektroskopie I: Ladungstransfer

MO 2.6: Talk

Monday, March 4, 2002, 15:15–15:30, HS 15/E07

Proton Transfer and Internal Conversion of o-Hydroxybenzaldehyde: Coherent versus Statistical Excited State Dynamics — •Tanja Bizjak, Kai Stock, Stefan Lochbrunner, and Eberhard Riedle — LS für BioMolekulare Optik, Sektion Physik, Ludwig-Maximilians-Universität München

The intramolecular excited state proton transfer (ESIPT) and internal conversion (IC) of o-hydroxybenzaldehyde were investigated by transient absorption measurements with 30 fs time resolution and quantitative fluorescence spectroscopy. A 45 fs delayed rise of the product emission and coherent vibrations indicate that the ESIPT is a ballistic motion of a well defined wavepacket along skeletal coordinates of the H-chelate ring. The IC proceeds as thermally activated process over an energy barrier of about 200 meV caused by an avoided crossing between the ππ*- and πσ*-state. The IC is sensitive to the total amount of vibrational energy but not to the energy content of the modes directly excited by the ESIPT. From this it is concluded that the coordinates involved in the ESIPT and in the IC are orthogonal.