F′ Type New Absorption Bands Associated with Complex Centers in Alkali Halide Crystals

Abstract

New absorption bands in KCl and KBr crystals are observed in near infra red region. It is considered that they arise from F′ type centers which consist of R₁, R₂ or M center and one more electron. F′ type bands appear during the process of F→F′ conversion in the crystal containing complex centers, and they are located at 1.60 μ, 1.72 μ, 2.15 μ and 1.49μ, 1.60μ, 1.94μ in KBr and KCl crystals, respectively. F′ type centers are thermally unstable than F′ center. These centers are called R₁′, R₂′ and M′.