Bonn 2000 – scientific programme
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MO: Molekülphysik
MO 20: Poster II: Ultraschnelle Dynamik
MO 20.3: Poster
Thursday, April 6, 2000, 17:00–19:30, Aula
Study of the phonon dynamics in the electronic ground state of polydiacetylenes with frequency–resolved femtosecond CARS — •T. Chen, A. Vierheilig, P. Waltner, A. Materny, and W. Kiefer — Institut für Physikalische Chemie der Universität Würzburg, Am Hubland, 97074 Würzburg
Frequency–resolved femtosecond CARS was applied to
polydiacetylenes to investigate the dynamics of phonons of
different vibrational modes in the electronic ground state.
At time zero one pump and the Stokespulses prepare a
wave packet composed of several phonon modes in the
electronic ground state. In the experiments presented, these
are ν2, ν3 and ν4. After a
time delay τ2 the wave packet is probed by the second
pump pulse. The anti-Stokes signal is dispersed in a
spectrometer and detected by an optical multichannel analyzer
(OMA) to yield information about the contribution of the three
coherently excited modes. When the delay time between the
first pump and Stokes pulses is negative or the wave-vector
difference of the first pump and Stokes lasers is vertical to
the backbone of the polydiacetylenes, the signal corresponding
to the ν3 and ν4 modes is stronger. When
the delay time between the first pump and Stokes pulses is
positive or the wave-vector difference of the first pump and
Stokes lasers is parallel to the backbone of the polydiacetylenes,
the signal corresponding to the ν2 mode is dominant.
We discuss a possible application for the optimation of
the generation of the coherent population in different vibrational
states of polyatomic molecules. Relaxation times and
intramolecular vibrational energy redistribution(IVR) are
analyzed.