Düsseldorf 2007 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 24: Femtosecond Spectroscopy III
MO 24.5: Vortrag
Dienstag, 20. März 2007, 15:30–15:45, 6C
Early excited state dynamics of β carotene near a conical intersection detected by Pump – Degenerate Four Wave Mixing (Pump – DFWM) — •Jürgen Hauer, Tiago Buckup, and Marcus Motzkus — Physikalische Chemie, Philipps-Universität Marburg, D-35032 Marburg, Germany
The early femtosecond dynamics on the electronically excited states of carotenoids play a crucial role in photosynthetic light harvesting. For understanding the evolution of β carotene near the conical intersection between its first two excited states, it is necessary to study the interplay between electronic and nuclear dynamics. We use a time domain method (Pump – DFWM [1]) yielding both time resolved excited state molecular Raman modes and information on the development of the involved electronic states.
Degenerate Four Wave Mixing (DFWM) has already proven to be a versatile tool for studying and controlling vibrational dynamics on β carotene’s ground state. [2]. Introducing an additional pump pulse preceding the DFWM – sequence, allows studying excited state vibrations. The technique delivers a time resolution only limited by the duration of the employed ultrashort pulses (sub 20 fs) and a spectral resolution better than 20 cm−1.
Since the DFWM - signal shows a decay time constant depending on the electronic state under investigation, the experiment also yields results on population dynamics near the conical intersection.
[1] Hornung et al., Chemical Physics Letters 402 (2005) 283–288
[2] Hauer et. al., Chemical Physics Letters 421 (2006) 523–528