Intramolecular and intermolecular dynamics in molecular liquids through femtosecond time-resolved impulsive stimulated scattering

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Abstract
Recent femtosecond time-resolved impulsive stimulated scattering experimental results from molecular liquids are reviewed and new data are presented. Three main areas are discussed. First, the inertial molecular motions of simple liquids (CS2, benzene) are observed. The results can be interpreted in terms of intermolecular librations, which in some cases are clearly manifest in the form of oscillatory time-dependent responses. The temperature-dependent intermolecular librational frequency and dephasing dynamics in CS2 liquid are determined. The data suggest that dephasing is predominantly inhomogeneous, and permit estimation of the extent of inhomogeneity in the librational frequency. Second, intramolecular vibrational oscillations are monitored directly in real time. The data are influenceed by both molecular vibrational and orientational dynamics. These experiments make possible time-resolved spectroscopy of vibrationally distorted molecules in well defined nonequilibrium configurations. Finally, the general occurrence of impulsive stimulated scattering whenever an ultrashort light pulse passes through a Raman-active medium is discussed