Thermally Assisted Tunneling: An Alternative Model for the Thermoluminescence Process in Calcite

TL;DR

This paper explores a thermally assisted tunneling model to explain thermoluminescence in calcite, considering effects of gamma and UV radiation, and identifies specific electron trapping centers and their behaviors.

Contribution

It introduces an alternative thermally assisted tunneling model for calcite's thermoluminescence, incorporating experimental data on radiation effects and electron traps.

Findings

TL peaks at 150, 245, 320°C identified

TL decay follows a t^{-1} law under UV illumination

Electron traps include carbonate ions and Mn^{2+} signals

Abstract

In this work we investigate the effect of gamma and ultraviolet radiations on the thermoluminescence of Brazilian calcite. The irradiated samples presented three TL peaks at 150, 245 and 320^oC (at a linear heating rate of 1.8^oC/s), with a main emission band centered at 615nm due to the ^4G \to ^6S transition of the Mn^{2+}. The irradiated samples presented, besides the Mn^{2+} signals, three lines related related to carbonate groups. The thermal treatment and the irradiation effects on the ESR signal lead to the conclusion that (CO_3)^{3-}, stabilized in two different symmetries, and the (CO_2)^{-} ions are the electron trapping centers. It was found that the TL peaks follows a t^{-1} decay as a function of the UV illumination time. An alternative model for the TL emission of calcite is discussed, considering that the recombination of charges is processed via a thermally assisted tunnelling mechanism.