EXPERIMENTAL STUDIES OF F 3 + COLOR CENTERS IN LiF CRYSTAL

In this paper, we describe systematically some experimental results of the optical characters of the creaion of F 3 + centers in LiF crystal by electron bombardment under different conditions. The relative density between F 3 + and F 2 centers are analysed from fluorescence spectra. The experimental results show that irradiation temperature plays an important role in the creation of F 3 + and F 2 centers and affects the relative density of F 3 + and F 2 centers. The main results are as follows: (1) Irradiation at liquid nitrogen temperature and then warming up to room temperature in the dark can create F 3 + canters with high density, which can be seen from the fluoreseence spectra, as fluorescence of F 3 + centers centered at 530 nm is much stronger than that of F 2 center (670 nm) and fewer N centers and R centers are presented in absortion spectra. (2) From dynamic fluorescence spectra, it can be shown that in the samples irradiated at liquid nitrogen temperature, the density of F 3 + centers increase rapidly when F 2 + centers decays. But in the samples irradiated at room temperature the growth of F 3 + and F 2 centers are approximatly with the came rate. (3) We observd the band width and double pike structure of the fluorescence excitation spectra of F 3 + and F 2 centers.