Berlin 2005 – scientific programme
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MO: Molekülphysik
MO 35: Quantum Control II
MO 35.1: Talk
Monday, March 7, 2005, 16:30–16:45, HU 2091
Controlling vibrational wave packets in condensed phase: Dispersion and coherence for Br2 in solid Ar — •Markus Gühr, Heide Ibrahim, and Nikolaus Schwentner — Institiut für Experimentalphysik, Freie Universität Berlin,Arnimallee 14 , 14195 Berlin, Germany
Interferences in vibrational wave packets of Br2 molecules are controlled in presence of a solid Ar environment that provides decoherence. By applying a negatively or positively chirped excitation pulse, one can set the clock backward respectively forward in the wave packet propagation with respect to dispersion. Based on this mechanism, we present a general scheme to record vibrational decoherence. Wave packets are spatially focused at at a time Topt by applying negatively chirped pulses. From the focussing contrast, we determine a vibrational dephasing time on the electronic B state of Tdephvib = 3 ps. We use positively chirped pulses to bring the formation of fractional revival structures forward in time with respect to Tdephvib. By exciting four distinct vibrational levels with such a pulse, we observe a 1/6 revival indicating the vibrational coherence time Tvib4 for these four levels. The required positive chirp prolonges the pulse duration by a factor of ten to Δτ = 300 fs. Electronic dephasing with the time constant Tdephel restricts the revival control fidelity to parts of the pulse with Δ τ < Tdephel, which allows to derive Tdephel > 300 fs.
[1] M. Gühr, H. Ibrahim and N. Schwenter, Phys. Chem. Chem. Phys. 6 (2004) in print