Düsseldorf 2007 – scientific programme
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MO: Fachverband Molekülphysik
MO 56: Poster: Femtosecond Spectroscopy
MO 56.3: Poster
Thursday, March 22, 2007, 16:30–18:30, Poster A
Collision-induced decay of rotational coherence of N2-molecules — •Philipp Giese, Nina Owschimikow, and Nikolaus Schwentner — FU Berlin, Institut für Experimentalphysik, Arnimallee 14, 14195 Berlin
Interaction of the anisotropy polarizability Δα of a molecule
with a short and intense linearily polarized laser pulse induces a
transient recurrent alignment of the molecular axis along the field
dirction. The revivals of the rotational wave packet are probed via
the optically induced Kerr effect. In gases at atmospheric pressure,
the rotational coherence persists for several hundred ps. Populations
and phases are modified only by bimolecular collisions, which makes
gases an ideal model system to study the dynamics of alignment. We non-adiabatically create a rotational wavepacket using IR laser
pulses (785 nm) of 150 fs duration with a power density of 1012 W/cm2,
and subsequently monitor the collision-induced decay of the rotational
revivals in pure N2 as well as mixtures of
N2/O2 and
N2/Ar at pressures up to 3 atm. The experimental results
are compared with models [1] and [2] for the influence of the
environment. The investigations are extended to higher densities up
to molecular dopants in crystalline matrices.
[1] S.Ramakrishna, T. Seideman J. Chem. Phys. 124, 244503 (2006)
[2] B. Lavorel et al. J. Raman Spectr. 31, 77 (2000)