Frequency and time resolved light scattering on longitudinal phonons in molecular supercooled liquids

The coupling of the rotational dynamics of anisotropic molecules to longitudinal phonons gives rise to different effects in the interaction of light with supercooled liquids formed of such molecules. One is the opening of new light scattering channels in Brillouin scattering; this can alter the corresponding phonon lineshape. Another one is the possible appearance of a depolarized signal in transient grating experiments (TG), also called impulsive stimulated scattering. We give a brief theoretical description of these two effects for supercooled liquids formed of linear rigid molecules. We also present preliminary results on the analysis of such a TG experiment performed on m-toluidine.