The influence of irradiation temperature on the formation of F-aggregate centers in LiF crystals

F-aggregate centers induced in LiF crystals by thermal annealing after the neutron irradiation at pile temperature are quite different from those at 20 K irradiation; ionized F-aggregate centers are induced during the thermal annealing in specimens irradiated at 20 K, whereas only the neutral F-aggregate centers are induced in specimens irradiated at pile temperature. The formation mechanisms for 560 and 500 nm bands induced during the thermal annealing in specimens after irradiation at low (20 K) and pile temperatures are discussed. The formation diagrams for 560 and 500 nm bands are proposed as follows, respectively; F + F3+ → F4+ and F + F4 → F5 or F2 + F3 → F5. (auth.)