Decay Times, Fluorescent Efficiencies, and Energy Storage Properties for Various Substances with Gamma-Ray or Alpha-Particle Excitation

Abstract

The results of measurements of the decay time of light flashes induced by gamma-ray quanta, or alpha-particles by means of pulse distribution curves for various crystals, powders, and solutions are presented. The decay of organic substances can be described essentially by a single exponential; in addition, a small more slowly decaying portion is present. The decay of inorganic crystals can be represented by a sum of exponentials with time constants in different ranges. The results support a previous explanation of the lower efficiency of alpha-particles in producing fluorescence when compared to gamma-rays.Results on various activated inorganic crystals of integrated fluorescent light output under gamma-rays and peak height measurements under gamma-ray and alpha-particle bombardment are also presented. The relative integrated and peak height properties are not well correlated, neither are the responses to gamma-rays and alpha-particles. Such variations are associated with the different emission times of the crystals. It is found that CsBr and CsI activated with Tl are excellent crystals with respect to luminescent properties especially when volume is a factor. The capability of these crystals to store energy to be released later as light by light of longer wavelengths is also indicated. Very good storage and stimulation properties are shown only by NaCl crystals activated with AgCl.