Fundamental Absorption of Solid Solutions of Alkali Halides Containing KBr

The intrinsic absorption spectra of evaporated thin films of various solid solutions containing KBr are measured at liquid nitrogen temperature in the photon energy range from 6 to 10.5 eV. The systems KBr-RbBr, KBr-NaBr, and KBr-KCl and chosen. In KBr-RbBr system, positions of peaks shift fairly linearly with the change in concentration. In KBr-NaBr, bromine doublet peaks show a remarkable red shift, while triplet structure around 8.5 eV, which is characteristic of KBr becomes indistinct and merges into a single broad band with increasing NaBr content. In the system KBr-KCl, peaks for both KBr and KCl are present in the samples of mixtures, but the relative intensities change markedly in varying concentration. The results are discussed mainly in connection with the theories developed recently.