Emission curves vs charging conditions in phosphorescent pigments embedded in sintered glass: Is there a reciprocity law?

Applications of phosphorescent materials are derived from their light emission properties at short and long times since the end of stimulation. The enhancement of such properties affects its performance in safety signs systems. Light emission power is conditioned by the time of excitation and the illumination received by the phosphorescent material, so that the total incoming energy is the product of both. For a given spectral profile, there is at least one upper limit of storable energy, resulting in effects of saturation for high values of illumination and excitation times. This work examines the emission curves of phosphorescent pigments embedded in sintered glass, in experiments where the total incoming energy is kept constant for combinations of illumination and time, in order to analyze the existence and the degree of reciprocity between these pairs. In addition, using a simple model we simulate some of the results obtained experimentally.