Abstract

Intermolecular dynamics of Raman-active modes in liquids traditionally have been investigated using the frequency-domain technique of spontaneous light scattering (LS) spectroscopy. Because of the intense central Lorentzian feature present in the LS spectra of liquids, however, the extraction of detailed dynamical information on low-frequency vibrational resonances has proven difficult. In contrast, femtosecond nonlinear-optical (NLO) spectroscopies have exhibited significant advantages over spontaneous scattering techniques for probing the Rayleigh wing region of LS spectra. We report here the results of an extensive investigation into the dynamics of intermolecular vibrations in liquids. We utilize the recently developed technique of femtosecond Fouriertransform Raman (FFTR) spectroscopy,^[1] which eliminates many of the complexities associated with the analysis of data that is third- order in the applied optical field. The data presented here for benzene and several benzene derivatives reveal dynamical and spectroscopic information that previously had not been deduced from spontaneous LS studies. Therefore, these results represent a significant advance in the study of intermolecular dynamics in liquids.

© 1992 IQEC