Determination of color centers in CaF2 crystals by multiple gamma-ray irradiations

Color centers of CaF2 crystals subjected to three high-dose gamma-ray irradiation treatments were studied. Three absorption bands at 349, 409 and 478 nm are ascribed to the F interstitials through the variation in difference additional absorption values. The transformation of interstitial F atoms to F ions (F-i(-)) is demonstrated using data with increasing radiation dose. The decrease in the 600 nm absorption band and the occurrence of the 580 nm band correspond to F-2(+) center conversion to F center. The complex (F--F-i(0)) might be associated with the 962 and 1196 nm bands.