Luminescence at 400 and 440nm in sanidine feldspar from original and X-ray-induced defects

Abstract

The blue luminescence of feldspar crystals with molecular composition Ab38Or60An2 and high-sanidine X-ray diffraction pattern from Miocene rhyolite ash tuffs of the Twin Falls Volcanic Field (Idaho, USA) has been studied by high sensitivity thermoluminescence (TL) up to 400 1C at 2.5 1C/s and radioluminescence (RL) at room temperature. The natural thermally stimulated blue luminescence is composed by a single emission at 400nm at T4200 1C probably linked to defect centres at original chemical impurities. The 50 Gy X-ray-induced TL emission exhibits a very symmetric broad band centred at 440nm and 200 1C, attributed to unstable radiation-induced defects. The RL spectrum displays these two signals which can be explained since irradiation induces charge carriers, and subsequent electron-hole recombinations, in addition to optically active defect centres. The 400nm band seems to be useful for dose reconstruction purposes.