We have investigated phosphorescence, thermoluminescence, and photostimulated luminescence in manganese activated zinc silicate phosphors, both with and without arsenic doping. Both phosphorescence and photostimulated luminescence intensities are found to decay as the reciprocal of the time, a result which requires a different interpretation from that given by the usual model of electron release from a distribution of trap levels. To account for these results we propose a new model based on the radiative recombination of electrons and holes through tunneling from shallow traps or from excited states of the deeper traps. A simple expression is derived which describes the decay of both types of luminescence in phosphors under very general conditions for which tunneling is the dominant recombination mechanism. Excellent agreement between theory and experiment is found. © 1981 American Institute of Physics.