The Structure of the Long Wave Absorption Edge of Insulating Crystals

Abstract

A general process, by which light can be absorbed in insulators at frequencies less than the frequency corresponding to the energy gap, is considered. Using an Einstein model with a constant energy gap, calculation of such a process is made by means of the method of intermediate states. The results are tested for the case of cadmium sulphide, and agreement with experimental results is found to be good when allowance is made for mathematical approximations made in the calculations.