Two types of additional absorption spectra in CaF2 crystals

A study of two types of additional absorption spectra observed in colored CaF₂ crystals is reported. The spectral shape for the additively colored crystal is governed by the experimental conditions; during photochemical coloring, it depends on the thermal prehistory of the sample. In all cases, a spectrum consisting of bands at 370 and 560 nm appears in crystals having a band near 200 nm. An additional band appears at 560 nm in the Smakula spectrum at high-irradiation doses; there are three stages in the increase of this band with increasing dose. A similar dependence on the radiation dose is observed for the 560-nm band in synthesized CaF₂ crystals. It is suggested that this band is due to defects produced in the lattice during the irradiation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, Vol. 12, No. 4, pp. 56–64, April, 1969.