Changes in OSL properties of quartz by preheating: an interpretation

A study of OSL variation with preheat temperature showed, in a majority of cases, that OSL recorded at room temperature, increases above 200 degreesC before the normal drainage at higher temperature. To explain this behaviour, an alternative interpretation to the common 'electronic thermal transfer' mechanism is suggested, supported by a study of hydrothermally grown quartz crystals. This interpretation involves impurities in substitution of Si4+, specially Al3+, which are associated with species like, in the case of quartz, hydrogen (H+, in fact, OH-) and alkali ions (Li+, Na+, K+). These monovalent ions usually act as charge compensators and are mobile during heating. As a consequence of the mobility and a possible irreversible exchange between compensators, the number of radiative recombination centres associated with the OSL trap(s), observable within the detection spectral window used (250-400 nm), increases during preheating. This phenomenon could lead to a wrong ED determination. (C) 2000 Elsevier Science Ltd. All rights reserved.