Understanding the reasons for variations in luminescence sensitivity of natural quartz using spectroscopic and chemical studies

Abstract

Natural quartz from diverse provenances exhibit variations in their luminescence sensitivity (photon flux/mg Gy) that span over ten orders of magnitude. A range of factors (such as crystallization/recrystallization process, irradiation, thermal and optical history) that modify luminescence sensitivity have been considered to explain such differences in luminescence sensitivity. However, a clearly definable/identifiable reason is still awaited; such as, these large variations in luminescence sensitivity are related to commonly occurring luminescence quenchers/enhancers in natural quartz lattice. Towards this, quartz mineral grains extracts from different provenances and from varied depositional environments were examined spectroscopically using Fourier Transform infra-red spectroscopy (FTIR), optically stimulated luminescence (OSL), photoluminescence (PL), time resolved PL (TRPL) decay, thermoluminescence (TL) and the trace element analysis. The present study exhibited an anti-correlation between OSL sensitivity and water content in quartz (estimated through integrated intensity of normalized FTIR signal in the wave number region 3000-3600 cm-1), such that a sensitivity change of over 5 orders of magnitude corresponded to a change in integrated water absorption signal by 5 times, but in opposite direction. PL and TRPL results enabled further insights.