Stuttgart 2012 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 17: Femtosecond Spectroscopy IV

MO 17.3: Vortrag

Donnerstag, 15. März 2012, 11:15–11:30, V38.03

Possible involvement of multi-photon pathways in femtosecond transient absorption experiments on retinal-isomerization in Bacteriorhodopsin — •Jan Philip Kraack, Tiago Buckup, and Marcus Motzkus — Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany

The photo-isomerization of all-trans retinal in Bacteriorhodopsin (BR) is an important model-reaction in time-resolved spectroscopy on rhodopsins. Upon photon-absorption, the excited-state population decays within less than a picosecond to form the ground state photoproduct with high quantum yield around 0.6. An important issue in the interpretation of BR's photo-dynamics concerns observable dependences of the signal on intensities of excitation pulses.[1-2] Using hyperspectral transient absorption spectroscopy, we investigated the femtosecond reaction kinetics of BR for a series of experimental parameters. In particular, we find that excited state relaxation dynamics depend on the excitation wavelength over a broad energetic range of excitation (500-600 nm). Screening of excitation-pulse intensities influences the ratio between ground state bleaching- and photo-product signal. The results are discussed in the context of existing two-photon pathways for the generation of photo-products not participating in the active photo-cycle of BR.[3]

[1]Florean et al., PNAS 2009, 106, 10896. [2]Prokhorenko et al., J.Chem. Phys. 2011, 134, 085105. [3]Fischer et al. Biophys., J. 2005, 89, 1175.