Photochromism in Calcium and Strontium Fluoride Crystals Doped With Rare-Earths Ions.

This paper reports the absorption spectra of photochromic centers in \CaF2 and \SrF2 crystals doped with \Ce^3+ and \Gd^3+ impurities and thermal decay of the centers in temperature range 80–500 K. The ionized photochromic color centers are generated in crystals under low-temperature X-rays irradiation. These centers are transformed into photochromic color centers upon heating of crystals. All color centers decay at temperature about 500 K. [ABSTRACT FROM PUBLISHER]