Exciton Transitions in the Single Crystals of the Mixed Compounds CdBr2 - CdCl2

Normal incidence optical reflection spectra of the mixed system CdBr2- CdC12 have been measured at liquid nitrogen temperature in the region 4-10.5 eV. The spectral behavior has been explained based on the energy band scheme. The exciton bands appearing around the optical gap are interpreted in terms of optical transitions occuring at the γ point in the Brillouin zone. The sharp lines observed in the deep interband energy regions are related to the Z point. The upper valence bands are of halogen ρ-likecharacter.The valence band of Pz - like character has a large dispersion along Kz