Luminescence Processes Generated by Ionizing Radiation in KI and KI:Tl

Abstract

Undoped KI and thallium‐doped KI are irradiated with x rays at 78°K. Luminescence and energy storage, in the form of trapped electrons and holes, are produced during irradiation. After irradiation phosphorescence is observed at 425 mμ and stimulation with light gives an emission quite similar to that during irradiation with bands at 302, 370, and 425 mμ. It is suggested that the luminescence produced during irradiation is predominantly from recombination. In stimulation the 425‐mμ band characteristic of thallium grows and decays slower than the 302‐ and 370‐mμ bands characteristic of the KI host. It is suggested that the phosphorescence is the result of the direct recombination of I₂⁻ and Tl°, and that the same process is occurring during stimulation and irradiation. In addition it is observed that 370‐mμ emission produced during irradiation decreases in intensity with increasing temperature and that the 425‐mμ emission intensity increases. It is suggested that 370‐mμ emission decreases because of a radiationless transition and that 425‐mμ emission increases because of the increase of recombinations at thallium sites.