The theory of Raman scattering from crystals

Abstract

e theory of the Raman scattering by crystals is discussed and detailed calculations made of the spectra from sodium iodide and potassium bromide. Expressions for the dependence of the optical polarizability on the normal modes of vibration are obtained by using the shell model with anharmonic interactions between the electronic dipole moments. The absolute intensity of the spectra can then be obtained from the parameters of these models. The effects of the anharmonic interactions between the normal modes on the spectra are also discussed, particularly for the one-phonon spectra. Detailed calculations of the two-phonon spectra of sodium iodide and potassium bromide at several temperatures have been made. The intensities and shapes of the spectra are strongly dependent on the polarizations of the incident and scattered light and on the orientation of the crystal. The dependence on the orientation makes a direct comparison with the available experimental measurements impossible, but the frequencies of the experimentally observed peaks can be correlated with peaks in the calculated curves quite satisfactorily.