Optically stimulated luminescence emission spectra from feldspars as a function of sample temperature

An optically stimulated luminescence (OSL) signal can be obtained from many feldspars when they are stimulated using wavelengths from 800 to 1000 nm. The intensity of this emission generally increases with temperature over the interval from 50 to 200°C, and measurements of this phenomenon have been used to characterize the degree of thermal activation involved in the production of the OSL signal. Such measurements would be compromised if the emission spectra altered with temperature. In order to test whether this is a significant problem, the OSL emission spectra of a number of feldspar samples have been measured at various sample temperatures. A small but consistent shift of the peak emission wavelength to shorter wavelengths at higher temperatures is observed. However, the magnitude of this shift is sufficiently small that it will not affect measurements of the thermal activation energy. A systematic difference is observed between the thermal activation energies measured when using different emission wavelengths. In particular, the thermal activation energy of the emission at 400 nm is typically 0.11 eV. while that at 570 nm from the same samples is 0.03-0.05 eV. Several possible explanations for this difference are suggested and it is shown that one important difference is that the two emissions show different degrees of thermal quenching.