Light Sum of Phosphors under Thermal and Infra-Red Stimulation*

Abstract

The experiments reported deal with the recently discovered type of phosphor that shows a large amount of luminescence of visible light when irradiated with infra-red. The emission can be made to occur when the normal phosphorescence has decayed to a negligible value. The light sum, or area under the decay curve, of such phosphors under infra-red stimulation is of the order of 1000 microlambert minutes. Measurements are reported for the light sum when the sample is irradiated with infra-red and when it is heated. In some phosphors the infra-red light sum is from 15 to 30 times as great as the light sum obtained by heating. In others, it is about the same, or perhaps even less. Attention is called to the connection between these experiments and the “glow curve” experiments used to determine the distribution of electron traps in phosphors.