Spectroscopic investigation of F, F₂ and F₃⁺ color centers in gamma irradiated lithium fluoride crystals

Optical absorption and photoluminescence spectra were measured on gamma colored lithium fluoride crystals at five different irradiation doses. By accurate Gaussian best-fit procedures of the absorption measurements the peak intensity of F and M bands and the concentrations of F, F₂ and F₃⁺ color centers in gamma irradiated LiF crystals at different doses were obtained. A quadratic relationship between F and F₂ defect concentrations as a function of the irradiation dose was found. Photoluminescence measurements, excited by an Argon laser at 457.9 nm, were used to study the effect of the laser power on the F₂ and F₃⁺ emission spectra of gamma irradiated LiF crystals. The influence of the triplet state on the optical cicle of F₃⁺ color center was highlighted for several excitation laser power and the ratio of the transitions probability W₁ and W₂ to and from the triplet state was derived.