Hannover 2013 – scientific programme

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MO: Fachverband Molekülphysik

MO 10: Femtosecond Spectroscopy II

MO 10.2: Talk

Tuesday, March 19, 2013, 11:30–11:45, F 102

Coherent high-frequency vibrational dynamics in the excited electronic state of all-trans retinal derivatives — •Jan Philip Kraack, Tiago Buckup, and Marcus Motzkus — Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Deutschland.

Coherent vibrational dynamics in excited electronic state(s) of photo-active chromophores are of primary importance in the understanding of photobiology. Using pump-DFWM(1-2), we demonstrate for the first time the existence of coherent high-frequency modulations (> 1200 cm-1) in the excited electronic state of different retinal derivatives. All-trans retinal as well as retinal n-butyl Schiff-bases exhibit a partial frequency downshift of the C=C double bond mode from around 1580 cm-1 in the ground state to 1510 cm-1 in the excited state. In addition, a new vibrational band at ~1700 cm-1 assigned to the C=N- stretching mode in retinal Schiff-bases in the excited state is detected. The newly reported bands are observed only if the DFWM-spectrum is tuned to specific spectral regions of excited-state absorption. Implications regarding the observation of vibrational coherences in naturally occurring retinal protonated Schiff-bases in rhodopsins are discussed. (1)Kraack et al., PCCP 2012, 14, 13979. (2)Buckup et al., ABB 2009, 483, 219.