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MO: Fachverband Molekülphysik

MO 22: Femtosecond Spectroscopy 3

MO 22.7: Vortrag

Freitag, 27. März 2015, 12:30–12:45, PH/HS1

Reaction-sensitive tracking of ultrafast chemical reaction dynamics with pump-dump spectroscopy — •Alex S. Duarte, Giovanni Bassolino, Christoph Schnedermann, Jongmin Lim, Torsten Wende, and Philipp Kukura — Physical & Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ

The retinal protonated Schiff base (RPSB) chromophore has become a paradigmatic photochemical system due to its widespread involvement in biological photoreceptors. One of the most puzzling and most studied aspects of RPSB photochemistry is the dramatic increase in reaction speed and yield in the protein over the solution environment, which has been attributed to a specific interaction of the chromophore with an evolution-optimised protein pocket.

Here, we combine excitation of RPSB in solution with a resonant 20 fs optical pulse followed by a 10 fs dump pulse that only serves to control the excited state population. By monitoring the photoproduct formation through changes in the transient absorption spectrum of RPSB at long time delays (60 ps) as a function of pump-dump-delay we reveal the earliest excited state relaxation dynamics for both 11-cis and all-trans RPSB in solution. Remarkably, the experiment reveals an ultrafast (<100 fs) photoisomerization channel for 11-cis RPSB in contrast to all-trans RPSB, closely resembling the dynamic behaviour of 11-cis RPSB in rhodopsin during the first step of vision.