A model for thermoluminescence and related phenomena in PbSO4:Sm

A model for energy states in a typical crystal containing substitutional cations is reconsidered with emphasis on the behaviour of electrons normally occupying states in impurity levels in the forbidden band. The model is used to explain thermoluminescence after irradiation and field excitation, the fading of colour centres and the unusual type of luminescence kinetics for which the pre-exponential factor in the rate equation is inversely proportional to the dose. A method of finding activation energies from graphs of depolarisation current against temperature is used to find values for PbSO4:Sm. These and measurements from isothermal decays, glow curves, absorption and emission spectra are entered in an energy band diagram. (author)