Exciton Spectra of CuBr-CuCl Solid Solutions

Abstract

The absorption and emission spectra of thin films of CuBr-CuCl solid solutions have been measured at 8°K and 80°K. The peaks of the exciton absorption and emission bands shift continuously with the composition rate. At 80°K only the emission of the lowest energy exciton is observed. Emission lines at 3899A in CuCl and at 4204A in CuBr are both due to the bound exciton and are called the I ₁ emission. The line width of the I ₁ emission line is broadened considerably in solid solutions. This can be interpreted as arising from the localized nature of the I ₁ exciton and the statistical fluctuation of the numbers of two kinds of negative ions within the region where the exciton is localized. The radius of the bound exciton is estimated as∼17A. The absorption band of the Z ₃ exciton has an exceptional large width in solid solutions in which no spin orbit splitting takes place.