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MO: Fachverband Molekülphysik

MO 24: Poster: Femtosecond spectroscopy

MO 24.2: Poster

Thursday, March 17, 2011, 16:00–18:00, P2

Interference phenomena in ultrafast spectrally resolved Degenerate Four-Wave-Mixing — •Jan Philip Kraack, Marcus Motzkus, and Tiago Buckup — Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany.

Homodyne-detected, spectrally-resolved Degenerate Four-Wave-Mixing (DFWM) with femtosecond pulses is an advantageous spectroscopic technique for the investigation of vibrational coherence dynamics. However, the homodyne detection method results in interferences between contributing response pathways. This has significant impact on the signal dynamics and their interpretation: (i) Interference between vibrational coherence pathways results in combination frequencies (beating) between molecular normal modes. This implies both sum and difference frequencies of the chromophore normal modes. (ii) Interference between non-oscillatory population and vibrational coherence dynamics affects the time-evolution of the wave packet signal intensity. (iii) Interference between response pathways from ground and excited electronic states can dramatically affect the signal dynamics. In this regard, we apply femtosecond DFWM to several molecular systems in solution and demonstrate that interference and normal mode contributions show a different dependence on the delay between excitation pulses and their phase-modulation (chirp). We additionally show that interference contributions provide information about vibrational dephasing time constants and spectrally overlapping ground and excited state absorption bands.