Emission probabilities and energies of γ-ray transitions from the decay of 235U

Abstract

To aid in the precise quantitative assay of 235U by means of γ-ray spectrometry, we have remeasured the emission probabilities of the γ radiation associated with its decay. The decay-rate calibration was based on the calibration of a standard solution by the U.S. National Bureau of Standards. The γ-ray emission rates and energies were measured with calibrated Ge spectrometers. The energy values obtained for six prominent γ-rays are 25.509 ± 0.009, 84.221 ± 0.004, 143.768 ± 0.003, 185.722 ± 0.004 and 205.318 ± 0.004 keV and the γ-ray emission probabilities determined for the five lines above 50 keV are 6.84 ± 0.10, 11.01 ± 0.08, 5.12 ± 0.04, 57.2 ± 0.5 and 4.96 ± 0.05 photons per 100 decays, respectively. The γ rays at 25 and 84 keV are produced in the decay of the 25-h daughter, 231Th, while the others are from the decay of 235U.