Thermoluminescence emission from localized recombination model

A simple model of thermoluminescence (TL), in which the trap and the recombination centre exist in the same defect complex, is assumed. It is called the localized recombination model (LRM). The analytical expression derived for this model turns out to be of first order irrespective of whether the system is recombination dominant or retrapping dominant. In this paper TL glow curves are calculated for this model using analytical as well as numerical techniques. The results show the following: (1) the glow curves calculated by the two techniques coincide with each other. However in retrapping dominant cases, the initial assumptions made by the original proponents of the model in deriving the analytical expression are not found to be valid, which apparently invalidates the analytical expression. This contradiction is reconciled in the paper and a new criterion is found for the validity of the analytical expression. ( 2) Even though the glow peaks of LRM always obey first order kinetics, their shapes may be typically of non-first order particularly when the value of s'/beta is below about 10(6), where s' is the pre-exponential factor and beta is the linear heating rate. In view of these findings it is emphasized that kinetic analysis of TL glow curves of real materials carried out purely on the basis of shape factor may lead to dubious results. It is recommended that a glow peak may be assigned non-first order only when dose dependence of peak temperature is observed.