Storage of Energy in Beryllium Oxide

The photostimulated ultraviolet emission of x-ray excited BeO has been measured as a function of the wavelength of the incident light. A maximum of emission occurs for a stimulating wavelength of ∼4100 A. Experiments are described which are interpreted as showing the presence of doubly occupied traps in BeO which are analogous to the $F$-centers of the alkali halides. Some discussion concerning energy storage in NaCl(Ag) is included.