Abstract

The absorption spectrum of CaF2 crystals containing color centers was investigated as a function of temperature and time elapsed after having been irradiated with x-rays under various conditions. A weak absorption band previously unobserved has been found near 2280A. The intensities of the four absorption bands of crystals irradiated at room temperature decreased to the same extent after having been heated at various temperatures for various time intervals. Irradiation with light at room temperature does not cause any appreciable bleaching. At elevated temperatures the bleaching rate is increased by light. The color of the absorbed light does not however produce any preferential bleaching of any one of the bands. The type of decay and the energies involved were calculated from results obtained by bleaching the crystals at several temperatures. In view of these facts, it would seem that the bands are due to either one type of center, or else to several types incapable of existing independently. The results of the computation of the number of color centers responsible for three of the bands are not incompatible with this point of view.