Spectroscopic investigation of F, F2and 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.