Thermoluminescence governed by the Auger-recombination process

In the present work, we study the possibility that a thermoluminescence (TL) peak is governed by the effect of Auger recombination, an effect which has been considered for other luminescence phenomena. In Auger recombination in the form of interest here, two conduction-band electrons are involved in the recombination of one of them with a hole in a center. The two electrons collide in the presence of the center, one loses energy and recombines, yielding a TL photon, and the other gains energy and speeds away. As mentioned with regard to other luminescence phenomena, in this case, in the set of differential equations governing this process, a term proportional to the square of the free-electron concentration should be included in analogy to the law of mass action. The relevant set of simultaneous differential equations has been solved numerically for feasible sets of parameters. The results yield a relatively narrow TL peak which is somewhat asymmetric, with the fall-off half being larger than the low-temperature half. Under appropriate conditions, the set of equations is shown to reduce to an approximate third-order kinetic equation, the solution of which has a very similar symmetry. The third-order approximate curve has an effective activation energy which is twice as large as the original. Such asymmetric peaks have been described in the literature. Also, when using standard peak-shape methods for evaluating the effective activation energy and frequency factor very high values of these magnitudes have been found due to the narrowness of the simulated peak. This model may explain the occurrence of such TL peaks previously reported in the literature. Also is discussed the possible concurrent regular Randall-Wilkins recombination and Auger recombination within the one-trap-one-recombination center (OTOR) model. In another version of the model, an additional thermally disconnected trap is considered. With certain sets of parameters, the simulations yield a cubic dependence of TL intensity on the excitation dose, an effect previously reported in some materials.