Observations of thermal transfer and the slow component of OSL signals from quartz

The thermal transfer optically stimulated luminescence (OSL) signals of bleached samples of sedimentary quartz are investigated using repeated heat/OSL measurement cycles with different heating temperatures ranging from 200 to 360 degrees. Under optical stimulation, the thermal transfer OSL decays with stimulation time. A strong correlation is observed between the initial part and the final part of the OSL decay curves. This relationship is dependent on the heating conditions and thermal history of the sample. Our results suggest that the thermal transfer OSL is due to the retrapping of charges that originated from optically insensitive traps by thermal release during heating, and not from the slowly bleached component associated with bleachable traps. Two kinds of OSL traps are involved into the thermal transfer, one is corresponding to the 325 degrees TL peak and the other is related to more stable traps. The thermally transferred signals can be distinguished from dose-generated signals by making repeated measurements of thermally transferred OSL decay curves.