The intensities of the Raman lines in carbon dioxide

Abstract

The polarisability of a molecule is assumed to be made up of the bond polarisabilities as functions of the inter-nuclear distances. It is pointed out that certain normal co-ordinates could be quadratic functions of some of the variations in the inter-nuclear distances which fact accounts for the appearance of overtone Raman lines assuming only first order variations in the bond polarisabilities. These ideas have been applied to the case of CO₂ and the intensity ratio of the Fermi split lines has been calculated which is in good accord with experimental observations.