New absorption bands in fluorites by heavy gamma irradiation

At least three new bands have been observed in the near infrared region of the absorption spectra of fluorites of different origin after heavy gamma irradiation in the range 106 to 109 R. Studies were also made with a sample of synthetically pure CaF2 crystal and the results indicate that the rare earth impurities abundantly present in the fluorites play an important role in the production of these new bands. The possibility of assigning these bands to some irradiation produced colloidal centres in the fluorites is discussed.