Frankfurt 2006 – scientific programme
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MO: Molekülphysik
MO 27: Poster: Femtosecond Spectroscopy
MO 27.2: Poster
Tuesday, March 14, 2006, 16:30–18:30, Labsaal
Molecular Decoherence in Solid Environments: Br2 in solid Ar — •Markus Gühr1,2, Heide Ibrahim1, and Nikolaus Schwentner1 — 1Institut für Experimentalphyik, Freie Universität Berlin, D-14195 Berlin — 2Stanford Synchrotron Radiation Laboratory, Menlo Park, California 94025-7015
The intramolecular wave packet dynamics on the electronic B (3Π0) potential of Br2 in solid argon is induced and interrogated by femtosecond pump-probe spectroscopy. An effective potential of the chromophore in the solid is derived from the wave packet period for different excitation photon energies. Deep in the potential well, it is consistent with vibrational energies from wavelength resolved spectra. At higher energies, the vibrational progression merges to a continuum and no potential can be derived from the high resolution spectra. In contrast, the time resolved spectra display pronounced wave packet dynamics which allow to construct an effective potential of the molecule in the matrix, even above the gas phase dissociation limit. This advantage of pump-probe spectroscopy is related to a reduced contribution of homogeneous and inhomogeneous linebroadening. A very large energy loss in the first collision of the molecule with the Ar crystal is observed. This strong interaction with the matrix is directly displayed in an experimental trajectory. Despite the strong energy loss, coherent wave packet oscillations can be observed after the collision. This is attributed to the special symmetry of the molecule-host system.