Thermally assisted tunneling: An alternative model for the thermoluminescence process in calcite - art. no. 014105

In this work we investigate the effect of gamma and ultraviolet radiations on the thermoluminescence of Brazilian calcite. The irradiated samples pres ented three thermoluminescence (TL) peaks at 150, 245, and 320 degreesC, wi th a main emission band centered at 615 nm due to the (4)G --> S-6 transiti on of the Mn2+. The irradiated samples presented, besides the Mn2+ ESR sign als, three lines related to carbonate groups. The thermal treatment and the irradiation effects on the electron-spin resonance signal lead to the conc lusion that (CO3)(3-), stabilized in two different symmetries, and the (CO2 )(-) 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 alterna tive model fur the TL emission of calcite is discussed, considering that th e recombination of charges is processed via a thermally assisted tunneling mechanism.