Optical Probing of the Environment of F Centers in Deformed Alkali Halides

The formation of F centers upon Co⁶⁰ irradiation of KCl deformed at room temperature and at 77^∘{}K and the environment of F centers formed upon Co⁶⁰ irradiation of deformed KBr were studied by means of optical-absorption measurements with a Cary-14 spectrophotometer. Anomalies of the beta absorption band (exciton band localized at the F centers) and shift of the F-center peak toward blue were observed in deformed KBr at 10 and 80^∘{}K. The observed anomalies can be removed by a short annealing near 525^∘{}K. Both the dichroic behavior of the beta band and the energy shift of the F band are consistent with the hypothesis that the source of vacancies is the edge-dislocation dipoles from plastic deformation. The F centers formed upon Co⁶⁰ irradiation of deformed KBr are most probably located a few Burgers vectors away from the core of one member of the edge-dislocation dipole inthe compression region, a fraction of an interatomic spacing above the slip plane where the edge dislocation is situated.