Thermoluminescence spectra of rare earth doped Ca, Sr and Ba fluorides

The low temperature TL spectra of undoped alkaline earth fluorides consistently show a continuous broad band emission around 280-300 nm. The origin of this emission is related to the relaxation of the self-trapped exciton (STE) in the form of an F-H pair. In doped samples, the broad emission is quenched in favour of emissions from the rare earth (RE) impurity sites. The degree of quenching varies between the REs. The spectral measurements showed that the temperature of the glow peaks below room temperature is to a large extent independent of the RE impurity, although some effects are related to the concentration. Additionally, the host material has minimal effect on the glow peak temperatures, T_max. The scale of the observed differences in T_max between the three hosts is similar to the differences in annealing temperatures of the V_k and H centres in these hosts. Above room temperature, the glow peaks are specific to the added RE ions and do not show common peaks.