Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 10: Femtosecond Spectroscopy II

MO 10.1: Invited Talk

Tuesday, March 19, 2013, 11:00–11:30, F 102

Revealing coherent nuclear wavepacket dynamics in biological photoreceptors — Matz Liebel and •Philipp Kukura — Physical and Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford

Revealing the atomic motions associated with a chemical transformation to understand the basis of chemical reactivity and dynamics has been one of the most sought after experimental capabilities over the past decades. Transferring the original observation of coherent nuclear wavepacket dynamics in simple diatomics to more complex systems, however, has proved exceedingly difficult. A tremendously well studied example is the all-trans to 13-cis photoisomerisation of the retinal chromophore in bacteriorhodopsin. Despite being subjected to virtually every ultrafast spectroscopic technique, its excited state vibrational spectrum and coherent nuclear dynamics remain largely in the dark. We have developed a novel approach, termed population assisted impulsive Raman spectroscopy (PAIRS), to succeed in not only determining the vibrational spectrum of the reactive excited electronic state, but also the coherent evolution of the photon-induced nuclear wavepacket during the isomerisation reaction. Our results reveal the activation of hydrogen out of plane nuclear motion following relaxation out of the initially populated Franck-Condon region, an emerging trademark of highly efficient C=C isomerisation reactions. The simplicity of the technique, together with a complete lack of often encountered interfering background signals is likely to make PAIRS one of the premier tools for studying ultrafast chemical reaction dynamics.