OPTICALLY INDUCED F CENTRE-INTERSTITIAL RECOMBINATION IN GAMMA IRRADIATED KCl

Abstract
It is known that when gamma irradiated KCl crystals are illuminated with F light they show a luminescence with its maximum at about 440 nm. The same emission band appears in the thermoluminescence of these samples from LNT to 300 °C. Several KCl samples were gamma irradiated at room temperature. Afterwards they were heated at 100 °C till no light at 440 nm was observed. They were then cooled down to room temperature. Each sample was illuminated with F light during some interval of time, a different interval for each sample. While this was made, the variation of the F centre concentration and the light intensity were simultaneously measured. After this bleaching interval, the thermoluminescence of the sample up to 350 °C was obtained. It was found that the area (A_F) under the photoluminescence Gurve and the area (A_T) under the thermoluminescence curve verify A_F/β + A_T/α = F₀ + 2 M₀. It has been concluded that this photoluminescence is due to the recombination of F centres which are mobile under illumination with trapped interstitials. This light emission at 440 nm has been used to detect optically induced F centre migration in several experiments. The results support Lüty's proposal that the F* center is the mobile entity.