Effects of Gamma Irradiation on Actinide Ions in Calcium Fluoride

Abstract

Optical absorption and thermoluminescence measurements were used to study the effects of gamma irradiation on trivalent actinide ions in CaF2. Thermoluminescent glow curves for Np, Pu, Am, and Cm (and, for comparison, the lanthanides Er, Ho, and Tm) were measured between 100 and 300°K. These were found to be remarkably similar, with glow peaks occurring at nearly the same temperatures for each of the ions. High resolution measurements of the spectra of the thermoluminescence showed that the emission is similar to the fluorescence of the trivalent ions. Evidence is presented that the glow emission below 300°K originates from trivalent actinide ions in cubic sites. When the actinide-CaF2 crystals were irradiated at 300°K, the actinide ion was oxidized to the tetravalent state. A mechanism has been proposed to explain these observations.