Mn2+ transitions in the TL emission spectra of calcite

Thermoluminescence spectra of calcite, Iceland Spar and synthetic CaCO3, all containing traces of Mn, were recorded from 20 to 400oC covering the wavelength range from 200 to 800 nm. The glow peaks appear variously as broad orange emission bands or as line spectra. In agreement with earlier work, it is assumed that the recombination site always involves Mn ions. However, closer examination of the evidence indicates that the orange emission is not totally a transition from the lowest excited 4G(Tlg) state to the 6S ground state, as cited by all earlier authors. Instead, all the data for the emission near 600 nm are consistent with a more complex set of transitions, including those from upper levels down to other excited states. Tentative transition assignments are proposed for the various lines. Evidence for this radically different view is presented. (Author)