Hannover 2003 – wissenschaftliches Programm
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MO: Molekülphysik
MO 14: Koh
ärente Dynamik
MO 14.1: Vortrag
Freitag, 28. März 2003, 11:30–11:45, B 302
Collisions Cause Coherence — •Matias Bargheer, Markus Gühr, and Nikolaus Schwentner — Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin
The electronic excitation of a molecule with a femtosecond laser pulse results in the creation of a vibrational wavepacks. Many investigations focus on the question, how the vibrational and electronic coherence is destroyed by the surrounding of the molecule. Especially the frequent, and often dissipative, scattering events in dense environments like solids or liquids seem to promote the loss of coherence.
In this contribution we demonstrate that inelastic collisions of the molecular wavepacket with solvent atoms also creates new vibrational coherences. We analyze fs-pump-probe spectra on the I2 molecule embedded in a Kr solid at 20 K. The systematic tuning of pump and probe wavelength shows that scattering processes create vibrational wavepackets with an energy which is not initially populated by the laser pulse. Moreover, we show that the collision gives rise to vibrational coherence in an electronic state that is not excited by the pump-pulse, i.e. the coherence survives nonadiabatic decay to a new electronic state combined with large energy loss of more than 0.7 eV.