Hannover 2010 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 14: Femtosecond Spectroscopy II

MO 14.4: Vortrag

Mittwoch, 10. März 2010, 15:00–15:15, F 102

Discrimination between low-frequency structural dynamics and beating using pathway-selective Four-Wave-Mixing Spectroscopy — •Jan Philip Kraack^{1, 2}, Tiago Buckup¹, and Marcus Motzkus^{1, 2} — ¹Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany — ²Physikalische Chemie, Philipps-Universität, D-35043 Marburg, Germany

The coherent preparation of vibrational states and determination of their femtosecond time-evolution is a powerful method for investigating ultrafast dynamics in the condensed phase. In the context of nonlinear spectroscopy, it is challenging to discriminate between contributions of molecular low frequency modes and beating between high-frequency modes. In order to investigate molecular low-frequency modes and to elucidate the time-evolution of wave-packets on the sub-20 fs timescale we applied Degenerate Four-Wave-Mixing (DFWM) to bio-physically relevant samples (Bacteriorhodopsin, Retinal Protonated Schiff-Bases, β-carotene). DFWM is an ideal spectroscopic technique combining advantages of high time-resolution, homodyne signal detection and allowing additionally investigations of electronic coherence dynamics. The signal modulations are interpreted regarding ground- and excited-state dynamics as well as environmental effects. We present a method for discrimination between beating contributions and normal modes and clarify the origin of low-frequency modes in carotenoids. It is shown that electronic coherence dynamics allow the induction of wave-packets after up to more than 100 fs of pulse separation.