The Decays of Luminescent KBr and LiF

A photo-multiplier, together with electronic pulse techniques, has been used to investigate the luminescent decay of KBr and LiF after irradiation with x-rays, at various temperatures. Decay curves plotted on a log-log scale are linear for KBr at 21°C and for LiF at 21°C and 0°C, with an average slope of 1.2. The curves for KBr at 0°C and the temperature of dry ice and acetone have linear upper and lower parts, connected by an intermediate curved part. It is suggested that the upper linear part is due to the decay of $F^{\prime }$ centers, and the lower part to the decay of $F$ centers. The emission spectrum of KBr consists of 2 bands, a strong one centered at 4550A and a weaker one at 5300A, while that of LiF extends into the ultraviolet below 3000A.