COMPUTER-SIMULATIONS OF OPTICAL BLEACHING OF TL AND OSL SIGNALS

We describe the results obtained from a computer simulation of bleachi ng of thermoluminescence (TL), generation of phototransferred TL (PTTL ) and production of optically stimulated luminescence (OSL) during opt ical stimulation. The model used in these simulations includes shallow trapping levels, thermally ''active'' traps from which charge is ther mally excited during TL readout, deep thermally disconnected traps whi ch are stable during TL readout, radiative recombination centers and n on-radiative recombination centers. In the model described, optical ex citation of electrons is assumed to occur from the thermally disconnec ted traps only. Recombination of optically excited electrons with trap ped holes is an important aspect of the model. PTTL, TL and OSL curves are simulated as functions of absorbed radiation dose and as function s of illumination time during optical excitation. The results indicate that a model such as this, in which the key feature is the recombinat ion of freed electrons with trapped holes, cannot be discounted as the mechanism for optical bleaching, PTTL and OSL in sedimentary material s.