Kinetics decay and electron phototransfer in cerium-doped fluorite

Luminescence decay after excitation by nitrogen laser radiation of Ce3+-doped calcium fluoride crystal has been investigated. Prolonged afterglow was found to remain for 10 s following short decay of an intra-centre emission. The afterglow spectra were measured. In this case photoconductivity was not recorded. The phosphorescence takes place both in oxygen-free and oxygen-containing crystals. Kinetics of afterglow is described by hyperbola with indexes depending on sample preparation conditions, temperature of measurements, and emission wavelength. By irradiation with 2.07 eV (600 nm) light (peak of Ce2+-ions absorption band) luminescence burst was observed after preliminary nitrogen laser excitation of the crystal. Electron transfer from excited ions Ce3+ to non-excited ions Ce3+, which are the capture centres, in the process of photoexcitation could account for observed phenomena. The effect of electron transfer is considered as a result of the electron states overlap of absorptive centres and electron traps.