New Results on Ultrafast Coherent Excitation of Molecular Vibrations in Liquids

Coherent Raman probe scattering experiments are performed to study
dynamical processes of polyatomic liquids at 300 K. For single
homogeneous transitions the dephasing timeT 2 is readily obtained
from time resolved investigations. Spectral studies show an
interesting time dependent shift in scattered frequency. After the
excitaiton the vibrating molecules are shown to relax freely with
their resonance frequency. Multiple, equally spaced transitions
exhibit a beating phenomenon which provides the dephasing time and
the frequency interval between neighboring vibrational states.
Inhomogeneously broadened systems do not allow a ready
determination of the dephasing time by the present probing
technique. Previous experiments on the subject have to be
reconsidered.