Hamburg 2009 – scientific programme

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MO: Fachverband Molekülphysik

MO 13: Molekülphysik Poster 1

MO 13.10: Poster

Tuesday, March 3, 2009, 16:30–19:00, VMP 8 Foyer

The Role of Vibrational Hot States on Pump-DFWM and CARS Experiments — •Mahesh Namboodiri, Jörg Liebers, Vinu Namboodiri, Abraham Scaria, Günter Flachenecker, Ulrich Kleinekathöfer, and Arnulf Materny — Jacobs University Bremen, Germany

The dynamics of electronic excited states of the bromine molecular system can be investigated in detail using pump-DFWM (degenerate four-wave mixing) and CARS (coherent anti-Stokes Raman scattering) techniques. The pump-DFWM experiments revealed that, by varying the DFWM wavelength, two clearly separated vibrational wave packets with oscillation periods of 395 and 510 fs could be observed, which correspond to a clear spacing of excited vibrational modes in the B state. This is due to contributions from vibrational hot states in the electronic ground state (X). Quantum dynamical calculations showed that for a pump wavelength of 540 nm, the Franck-Condon overlap from the first vibrational hot state for the B ← X transition is considerably better than that found for transitions from the vibrational ground state of the X state. CARS experiments were performed in order to substantiate these findings. Here, the pump wavelength was kept fixed at 540 nm while both the Stokes wavelength and the temperature were varied. At higher temperatures an increase of hot state contributions to the observed B state dynamics was found. The detuning of the Stokes wavelength selectively probed the hot state contributions even at room temperature. The experimental and theoretical results were in good agreement with previous observations.