On the dose dependence prior and after stimulation with visible light of E' and Al-hole centres in sedimentary quartz: correlation and mechanisms

E’ and Al-hole centres are some of the most common and abundant paramagnetic defects in sedimentary quartz. Here we investigate the dose dependence of these defects before and after exposure to light by electron spin resonance (ESR). Unlike the Al-hole centre, known to have only radiation-induced formation mechanisms, the E’ seems to possess a response to gamma dose characterised by predominantly radiation-induced annihilation at lower doses (about 1000 Gy) and a predominantly radiation-induced formation at higher doses, at least in our investigated dose range (up to 40 kGy). We propose these dose response mechanisms to be governed by electron trapping by E’ itself and by hole trapping by the oxygen deficiency centre (ODC), known to be the main precursor of E’. We show that the ESR signals of both defects are linearly correlated during their formation as well as during their dissociation under both irradiation and sunlight exposure. We further show that there is a clear correlation between the light sensitive Al-hole centres (also known as the Al-hole bleachable part), and the amount of E’ produced after prolonged light exposure. This indicates a correlation between the holes released from Al-hole and those trapped by one of the two electrons in the ODCs producing E’. As such, the origin of the unbleachable part of the Al-hole signal resides in the availability of oxygen deficiency centres which are also dependent on the accumulated gamma dose