Precise measurements of the absolute γ-ray emission probabilities of 223Ra and decay progeny in equilibrium

Abstract

Precise measurements of the absolute γ-ray emission probabilities have been made of radiochemically pure solutions of 223Ra in equilibrium with its decay progeny, which had been previously standardised by 4π(liquid scintillation)-γ digital coincidence counting techniques. Two high-purity germanium γ-ray spectrometers were used which had been accurately calibrated using a suite of primary and secondary radioactive standards. Comparison of the activity concentration determined by the primary technique against γ-ray spectrometry measurements using the nuclear data evaluations of the Decay Data Evaluation Project exhibited a range of ~18% in the most intense γ-ray emissions (>1% probability) of the 223Ra decay series. Absolute γ-ray emission probabilities and standard uncertainties have been determined for the decay of 223Ra, 219Rn, 215Po, 211Pb, 211Bi and 207Tl in equilibrium. The standard uncertainties of the measured γ-ray emission probabilities quoted in this work show a significant improvement over previously reported γ-ray emission probabilities. Correlation coefficients for pairs of the measured γ-ray emission probabilities from the decays of the radionuclides 223Ra, 219Rn and 211Pb have been determined and are presented. The α-transition probabilities of the 223Ra have been deduced from P(γ+ce) balance using the γ-ray emission probabilities determined in this work with some agreement observed with the published experimental values of the α-emission probabilities.