Color Centers in CsBr Single Crystals Irradiated at Liquid-Helium Temperature.

The principal absorption bands induced by irradiation at liquid-helium temperature with x rays in CsBr crystals are the complex $F$ band and two overlapping $V$ bands at 435 and 497 mμ. In view of the dichroic properties of these $V$ bands, the most obvious model seems to be a ${\mathrm{Br}}_2^{-}$ molecule-ion lying in the $〈100〉$ directions. The two observed absorption bands would be due to two transitions in the same center. Regarding the bleaching properties, the $F$ center cannot be the only color center responsible for the structure of the complex absorption band. Hypotheses are proposed about the interactions between the $V$ and $F$ centers.