Relaxation processes and spectra in liquids and dense gases

Abstract

The spectral response of a molecule dissolved in a liquid or dense gas is calculated using a correlation function approach. It is shown that the characteristic spectra of the molecule can be used as a probe of the molecular motions and the dynamic structure effects. A method developed by Blume and Kubo which assumes the solute–solvent interaction parameter to be a stochastic process is employed. The induced Q branch in the vibration–rotation spectra of polar molecules is discussed as an example and the cases in which the rotational relaxation of the molecule is determined by either the dynamic structure or by collisional processes are obtained in the appropriate limits.