A theoretical model for a new dating protocol for quartz based on thermally transferred OSL (TT-OSL)

Recently a new dating procedure has been suggested, which is based on the thermally transferred optically stimulated luminescence (TT-OSL) signal that is measured after irradiated quartz is optically bleached and then preheated. Experimentally the TT-OSL signal was measured after a high temperature preheat (260 degrees C for 10 s) following an optical bleach at 125 degrees C for 270 s to deplete the fast and medium OSL components. The TT-OSL signal was measured for 90 s at 125 degrees C in order to avoid the effect of re-trapping of electrons in the 110 degrees C trap of quartz. The luminescence sensitivity changes were monitored by the OSL response to a test dose. In this paper, we use a modified version of a comprehensive model to simulate the complete experimental sequence of the new protocol, and to fit the experimental dose-response graphs of the OSL, TT-OSL and basic-TT-OSL signals for doses up to 4000 Gy. Two possible mechanisms for the production of the TT-OSL signals in this quartz are discussed, namely the double transfer mechanism suggested for the recuperation effect, and a single transfer mechanism in which the TT-OSL signal is due to the thermal transfer of charge from a "source trap" into the fast OSL trap of quartz. The results of the simulation indicate that the latter mechanism is more likely to be responsible for the observed TT-OSL dose growth in fine-grained quartz extracted from Chinese loess. (C) 2008 Elsevier Ltd. All rights reserved.