Raman intensities of lattice modes and the oriented gas model

Abstract

The applicability of the oriented gas model to the calculation of Raman intensities of molecular crystals is investigated. The basic implications of the model and its consequences are discussed. The polarized spectra of only 3 out of 11 crystals considered are compatible with the model. For these, quantitative calculations based on calculated eigenvectors give reasonable agreement with experiment, while the others are in clear disagreement with available data. It is shown that assignments of unpolarized spectra based on the model’s predictions may easily be erroneous. Some of the parameters affecting the calculation are analyzed, confirming the conclusion that the oriented gas model is not a reliable tool for assignment of Raman lattice bands of molecular crystals.