I. Introduction
A tunneling process can significantly affect the dynamics of a luminescence center excited state and consequently also the performance of luminescence materials. Its effectiveness strongly depends on the distance between the luminescence center and the host trap. Quantum tunneling was found to be a cause of “anomalous fading.” This phenomenon was observed some time ago in the luminescence decay of various materials used in thermally and optically stimulated luminescence dating [1]–[14]. Calculations based on tunneling between recombination centers and traps at randomly distributed distances can give inverse power-law decay of luminescence over many orders of magnitude [12], [15], [16]. An alternative explanation of anomalous fading can be given by the models of localized or semilocalized transitions regarding hole–electron pairs in irradiated materials [17], [18].