Nonresonant intermolecular spectroscopy beyond the Placzek approximation. I. Third-order spectroscopy

We present an instantaneous normal mode analysis of the intermolecular Raman-weighted density of states of CS2, including the effects of the second-derivative tensor of the many-body polarizability. Based on the results of these calculations, we suggest a set of minimal elements that are necessary for collective-coordinate models of polarizability dynamics in liquids. The effects of different scattering mechanisms, the tensor nature of the polarizability, and the complex relationship between derivatives of the polarizability for intermolecular modes are shown to be essential elements of such a model. (C) 1998 American Institute of Physics.