Influence of the infrared stimulation on the optically stimulated luminescence in four K-feldspar samples

Abstract

Many dating protocols involve combined measurements of thermoluminescence (TL), optically stimulated luminescence (OSL) and infrared stimulated luminescence (IRSL). Although the physics behind each stimulation mode is entirely different, it is possible that all of these stimulation modes act on the same set of electron trapping levels existing in dosimetric materials. Therefore, one might expect that the experimental results of the combined TL, OSL and IRSL measurements may be correlated. The present work deals with the correlation between IRSL and OSL signals. The experimental protocol involves an initial exposure of the irradiated sample to infrared radiation (IR) for various stimulation times, and then recording the continuous-wave OSL signal (CW-OSL) of the same sample. In this way one can follow how the exposure to IR influences the trapping levels responsible for the CW-OSL signal. The results of the experiments showed that the IR stimulation influences these trapping levels which are responsible for the fast components of the CW-OSL decay curve, and not the trapping levels responsible for the slow CW-OSL components. The IRSL decay curves are described by analytical equations derived from a localized tunneling recombination model. On the other hand, the CW-OSL decay curves were fitted successfully with either one of two following methods; Firstly they were fitted by using an analytical expression derived from the solution of the one trap one recombination center model (OTOR), which describes delocalized recombination processes. Secondly, the CW-OSL decay curves were also fitted successfully using the same analytical expressions used for fitting the IRSL decay curves, based on localized transition processes. A more detailed analysis of the CW-OSL signals for stimulation durations up to 100s, showed that the description of the CW-OSL using the localized tunneling recombination expression is superior to the description which uses the delocalized OTOR model.