Simultaneous Production and Bleaching of F Centers in KCl

KCl crystals are irradiated simultaneously with x rays and light, and then irradiated with x rays in the dark. The resultant $F$-band coloring is considerably greater than for crystals which were irradiated the entire time by x rays in the dark. The effect was studied as a function of the wavelength and intensity of the light and the temperature of irradiation. It occurs only for light in the $F$ band. As a function of light intensity, it increases monotonically and then saturates. The amount of light necessary is a strong function of irradiation temperature between 20 and 60\ifmmode^\circ\else\textdegree\fi{}C. The effect did not occur at liquid-nitrogen temperature. Optical and thermal bleaching experiments, for crystals which had been simultaneously irradiated and bleached before coloring, gave different results from those for crystals which were x-rayed in the dark only. There is some discussion of mechanisms.