Reflection Spectra of CdCl₂-CdBr₂Mixed Crystals in the Region of Band Gap Excitons

Reflection spectra have been measured on CdCl 2 -CdBr 2 mixed crystals in the region of band gap excitons using the cleaved surfaces. It is found that both the persistence and the amalgamation types of the spectral behavior upon making mixture can occur in this system. The behavior is interpreted in terms of the exciton transitions at the \( \) point from halogen p -like valence bands to a cadmium s -like conduction band: The amalgamation-type behavior comes from an admixture of the p z -state wave function to the \( ₄⁻\) valence states, and the persistence-type behavior is ascribed to the p x - and p y -like character of the \( ₅⁻\) and \( ₆⁻\) valence states.