Comparison of infrared spectrometric characteristics of Al-OH impurities and thermoluminescence patterns in natural quartz slices at temperatures below 0°C

Abstract

Radiation-induced luminescence phenomena were compared using various kinds of two-dimensional (2D) images. These included thermoluminescence (TL) color images, color center distributions, Al-impurity distributions measured using electron probe microanalysis, OH-impurity mappings using infrared-spectroscopy, and radioluminescence images. Additional measurements included on-line TL-spectrometry, and electron spin resonance (ESR). Comparing the OH-impurity patterns with the 2D luminescence images, the concentration of Li-related OH, molecular water, Al-OH and Al-impurities in quartz slices were found to be inversely correlated with the blue thermoluminescence (BTL)-images above room temperature. However, the BTL-glowcurve at low temperatures, from −196°C to room temperature, showed an intense BTL peak around −150°C, coincident with the rapid disappearance of hydrogen radicals observed using ESR spectra. It is proposed that hydrogen radicals, produced from radiolysis of OH groups and/or free water within quartz, can operate as quenchers of radiation-induced phenomena, mainly those responsible for the formation of Al-hole centers (AlO 4h +) 0 below −120°C. The similar eliminating action of Al-hole centers with mobile hydrogen radicals was confirmed using radioluminescence color images, from samples exposed at the ambient temperature, in agreement with the 2D TL-color images observed at temperature regions below −120°C. The concentrations of OH-groups and/or free water within the quartz were concluded to significantly affect radiation-induced phenomena of different origins.