Osnabrück 2002 – wissenschaftliches Programm

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MO: Molekülphysik

MO 4: Femtosekundenspektroskopie II: Wellenpaketdynamik und reaktive Prozesse

MO 4.1: Vortrag

Montag, 4. März 2002, 16:30–16:45, HS 15/E07

Ultrafast molecule - solvent interactions in dissociation and recombination dynamics: ClF in rare gas solids — •Matias Bargheer1, Jörg Pietzner1, Peter Dietrich2, and Nikolaus Schwentner11Experimentalphysik FU-Berlin, Arnimallee 14, 14195 Berlin — 2803-1000 Castle Hill Cres., Ottawa ON, K2C 3L7, Canada

We investigate the ultrafast dynamics of ClF in rare gas solids after excitation with UV femtosecond pulses.[1] The F atom is small enough to be photo-mobilized in rare gas solids while the larger Cl is trapped in the initial solvent cage. In this model system we study the influence of the solvent on ultrafast dynamics in a dissociative reaction and in the competing recombination pathways.

Excitation of ClF above the dissociation limit leads to rapid coupling of energy into the solvent. We observe the recombination dynamics enforced by the solvent cage, monitoring the Cl+F emission in fs-pump-probe spectra. The energy dissipation decreases by two orders of magnitude after reformation of the ClF bond. We follow the fragment dynamics after dissociation by monitoring e.g. the emission from Kr2+F. The trapping of F atoms in a neighboring cage is probed and ultrafast thermalization is observed.

We investigate the solvent-induced coupling of electronic states and ultrafast spin-flip within 500 fs is observed and compared to DIM-trajectory calculations. Polarization dependent pump-probe experiments yield depolarization of molecular orbitals on the same timescale.

[1] M. Bargheer, J. Pietzner, P. Dietrich and N. Schwentner, J. Chem. Phys. 115, 9827 (2001)

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