Thermoluminescence in NaCl Single Crystals Containing Copper and Calcium

Abstract

The charge carrier trapped centers responsible for the thermoluminescence in irradiated NaCl:Cu⁺ and NaCl:Ca²⁺, Cu⁺ single crystals have been detected by ESR. Cu²⁺ ions accompanying positive ion vacancies at their next nearest neighbor sites disappeared by heating the NaCl:Cu⁺ crystals at about 70°C, which corresponds to the temperature where the first glow peak appears. This indicates that the peak is due to the recombination of thermally released electrons and Cu²⁺ ions. The higher temperature glow peaks showed different emission spectra from that of the first peak, indicating that the mechanisms are different. The Cl₂^- molecular ions stabilized by the I-V (impurity-vacancy) dipoles and the D₁-like centers were observed in NaCl:Ca²⁺, Cu⁺ crystals, which work as the hole trapped species in thermoluminescence.