The inhibition of F-centre production in alkali halides caused by electron-trapping impurities

The rate of production of F centres in alkali halides, during the slow stage of coloration by ionizing radiation, is often reduced by electron-trapping impurities. The conditions for, and extent of, this inhibition are calculated on the assumption that F-centre production takes place via electron-hole recombination. The inhibition is determined by the dimensionless parameter S . For S << 1 there is little inhibition of the F-centre production rate, which is linearly dependent on n γ . When S = ½ the rate is reduced by a factor of two. For S << 1 the rate is much smaller than in the pure crystal, and depends on irradiation intensity, impurity concentration and crystal temperature. These various predictions are shown to be in good agreement with experiment.