OSL decay curves-relationship between single- and multiple-grain aliquots

In this paper experimental results and numerical simulations of fitting exponential functions to OSL decay curves are presented. The measurements show that the OSL decay curves of single grains of a sample can vary in decay form. Despite the fact that all grains have a different OSL decay forms it appears that the OSL decay curve of their sum can be well fitted with a small number of exponential components. The simulations confirm that if the OSL decay curves of single grains consist of single exponentials with varying decay constants and intensity, the OSL decay curves of multiple-grain aliquot can be fitted with one exponential or a sum of two exponentials. The discussion is then extended to LM-OSL curves where similarly the observation of a number of first-order components may be a manifestation of the heterogeneity of the sample. In the simulations, it is also shown that a stretched exponential function may very well fit a sum of exponentials being merely an indication of the heterogeneity of the sample. It is shown that the resolution of the fit of a sum of exponentials to a decay form is limited by the intensity fluctuations. The conclusion is drawn that interpretation of the form of CW- or LM-OSL should be accompanied by complementary measurements and it should be checked that the sample is homogenous, e.g. by investigating single grains.