Vibrational spectroscopy of partially disordered homogeneous systems

Abstract

This paper presents an analytical review of studies of the spectrooptical properties and structure of systems with various degrees of structural disorder. The main attention is devoted to the general experimental regularities in the temperature-phase behavior of the spectra for which there is no generally accepted explanation. The dynamics of the variations of the vibrational spectra of crystals are considered as the concentration of point defects increases to the melting point. The observed structural simplification of the spectra, the smearing and depolarization of the lines, the appearance of a continuum in the low-frequency region, and a number of other features are associated with the scattering and damping of phonon waves at defects, as well as with relaxation processes. The mechanism of the appearance and manifestations of orientational defects in crystals and the preservation of traces of orientational disordering in liquids are tracked over the spectra and are described by means of theoretical models.