Photostimulated Emission of Some Activated Alkali Halide Phosphors

The intensity of the photostimulated ultraviolet emission of x-ray excited phosphors of NaCl-Tl, KCl-Tl, NaCl-Ag, and KCl-Ag has been measured as a function of the wavelength of the incident light. The results indicate that, in the first thirty days following excitation at least, $F$ centers are primarily responsible for the storage of energy. Thus, the storage properties depend upon the nature of the host material, rather than upon the intentionally added activator. Evidence is also presented which seems to indicate the presence of a deep trap associated with the silver ions of KCl-Ag which has a period of decay comparable to that of the $F$ centers. Excitation, storage, and all measurements were carried out at 22°C. Polycrystalline materials, prepared by the writers, were used throughout the investigation.