The influence of ultraviolet light on luminescence (700–1000 nm) of LiF and LiF:ОН crystals irradiated in a nuclear reactor

The emission (700–1000 nm) and absorption (200–800 nm) spectra of LiF and LiF:ОН crystals irradiated in a reactor and by UV light, as well as subjected to combined action of UV light and mechanical stress, are studied. The aim of the work is to study the behavior of laser color centers in these crystals. In the range of 710–825 nm, diametrically opposite results are observed: namely, the F$_4$-like centers are highly stable in pure LiF and are rapidly destroyed in LiF:OH crystals. At the same time, the F$_3$ and F$_4$ centers are destroyed in both cases, while the F$_2^+$ and F$_3^-$ (825–925 nm) laser centers are efficiently accumulated. After subsequent storage in the dark at room temperature, we observed spontaneous decay of laser centers accompanied by an increase in the concentration of F$_4$-like centers and recovery of the microstructure of irradiated crystals.