Luminescence from natural fluorite crystals

Abstract Luminescence spectra are reported for a range of natural fluorite crystals of different colours which contain rare earth impurities. Whilst photoluminescence and optical absorption spectra reveal different impurities such as Ce, Eu and Sm, the thermoluminescence spectra are dominated by signals from Dy ions with only traces of emission from other impurities. The reasons for the apparent differences between photoluminescence, optical absorption and thermoluminescence analyses are discussed. Glow peak temperatures are similar in each sample, suggesting that the basic trapping sites are closely related; however, fading studies indicate that this is only partially correct. In all cases the thermoluminescence recombination sites involve rare earth ions. There is the possibility that the trapping and luminescence sites are not independent but part of large defect complexes.