Effect of Lead on the Room-Temperature Colorability of KCl

Abstract

The introduction of $F$ centers in Pb-doped KCl by ionizing radiation has been measured as a function of lead content for different radiation intensities. For the lowest intensity (gamma irradiation), as little as 0.5-ppm impurity caused a marked decrease in the late-stage coloration and less than 100 ppm completely suppressed the late stage. Lead impurities are less effective in decreasing late-stage colorability when higher irradiation intensities (electron irradiation) are used. These results suggest that previously observed variations in the late-stage coloration characteristics could have been due to trace amounts of impurities of the order of 1 ppm. Furthermore, it is suggested that these trace impurities are not depleted during irradiation, but affect the late-stage colorability by acting as electron or hole traps, or as recombination centers.