PHOTOIONIZATION AND PHOTOCHEMICAL PRODUCTION OF COLOR-CENTERS IN CE3-DOPED AND CE3+NA+-DOPED CAF2()

The photoionization of Ce3+ in CaF2 has been reinvestigated with CaF2: Ce3+ and CaF2:Ce3+, Na+. Irradiation of the singly doped crystals with 308-nm light at room temperature produces Ce2+. However, at 80 K, we found no Ce2+ and observed only that the F- interstitial charge compen sator moved from the (001) site to the (111) site. (Units are a/2, the unit cell dimension.) In the doubly doped crystals, we observed the p roduction of Ce2+ at 80 K. Diffusion processes at higher temperatures lead to formation of other color centers. A mechanism that accounts fo r these observations is proposed.