|Philip J. Kraack, Tiago Buckup and Marcus Motzkus
Physikalisch-Chemisches Institut, Ruprecht-Karls Universität, Im Neuenheimer Feld 229, D-69120 Heidelberg, Germany
Probing vibrational coherence (wave packet) dynamics in time-resolved optical signals is a major issue of femtosecond spectroscopy. This is because such dynamics can directly report about molecular structure, transient structure evolution as well as interactions between for instance bio-physically active chromophores and their environment. The investigation of such dynamics is therefore of crucial importance in highly organized biological samples. Among a series of spectroscopic techniques, (Pump-) Degenerate Four-Wave-Mixing has proven its use towards elucidation of wave packet dynamics even in complex systems such as carotenoids from light-harvesting complexes or photo-chromic membrane proteins.[2-3] We present investigations of wave packet dynamics in the all-trans retinal chromophore both in solution and in natural environment (Bacteriorhodopsin). These signals with periods ranging from a few tens to hundreds of femtoseconds contain important information about electronic excited state and ground state dynamics and can be used to resolve the primary relaxation dynamics of the molecule upon photo-excitation.