In this work we investigate the effect of gamma and ultraviolet radiations on the thermoluminescence of Brazilian calcite. The irradiated samples presented three thermoluminescence (TL) peaks at 150, 245, and $320°\mathrm{C},$ with a main emission band centered at 615 nm due to the ${}^4{\overrightarrow{\mathrm{G}}}^6\mathrm{S}$ transition of the ${\mathrm{Mn}}^{2+}.$ The irradiated samples presented, besides the ${\mathrm{Mn}}^{2+}$ ESR signals, three lines related to carbonate groups. The thermal treatment and the irradiation effects on the electron-spin resonance signal lead to the conclusion that $({\mathrm{CO}}_3{)}^{3-},$ stabilized in two different symmetries, and the $({\mathrm{CO}}_2{)}^{-}$ ions are the electron trapping centers. It was found that the TL peaks follow 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 tunneling mechanism.

• Received 8 June 1999

DOI:https://doi.org/10.1103/PhysRevB.64.014105