Origin of ultrafast dynamics in time-resolved impulsive stimulated Raman scattering (ISRS) from molecules in liquids.

Abstract

1. One of the features in ultrashort time-resolved nonlinear coherent scattering spectroscopy is creation of a transient intermolecular coherence in molecular liquids. 1,2 For example, teraheltz quantum beats appear in time-resolved coherent anti-Stokes Raman scattering (CARS) and time-resolved impulsive stimulated Raman scattering (ISRS) profiles as a result of the creation of the intermolecular vibrational coherence. Such time-resolved profiles provide us information on the mechanism of the intermolecular dynamics. Recently, Nelson group has reported the time-resolved ISRS profile of dibromomethane liquid.2 The most distinctive feature is the appearance of 5.2 teraheltz quantum beat with two apparent decay components. The quantum beat is associated with the creation of intermolecular, vibrational coherence between Raman transitions of 173 cm-1 bending mode of dibromomethane molecules at different sites. The time-development behavior was not clarified from the microscopic point of view.