Hannover 2003 – wissenschaftliches Programm

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MO: Molekülphysik

MO 6: Poster I

MO 6.18: Poster

Dienstag, 25. März 2003, 16:00–18:30, Lichthof

Experiments with Phase-Locked Femtosecond Pulses — •Matias Bargheer, Mizuho Fushitani, Markus Gühr, Toni Kiljunen und Nikolaus Schwentner — Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin

We generate phase-locked pulse-pairs by sending femtosecond laser pulses through a Michelson interferometer, where one end-mirror can be moved and stabilized with interferometric precision. When the spectrum of a pulse pair with delay τ is recorded with a monochromator, spectral interferences with a spacing of ν =1/τ are observed. The pulse-pairs are applied to electronic excitations of molecules. Depending on the phase of the pulse-pair, the interferences are in or out of resonance with the vibrational absorption lines in the excited state of the molecule, which leads to a maximal or minimal excitation yield, respectively. In the time domain, the first pulse excites a vibrational wavepacket and the second pulse excites another wavepacket which interferes constructively or destructively [1]. Alternatively, pulses with the same spectrum and/or time structure are produced in a pulse-shaper with amplitude and phase modulation.

The of interference of wavepackets in molecules with different coupling to the environment is studied in this way. The system Cl2 in Ar solids is a suitable candidate, because the absorption spectrum exhibits regions with clean zero phonon lines (undisturbed wavepacket) and regions with increasing phonon sidebands (wavepacket coupled to surrounding). This situation promises to yield a deeper understanding of the problem of decoherence.

[1] J. Chem. Phys. 95, 1487 (1990)

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