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

S M Collins; A K Pearce; P H Regan; J D Keightley

doi:10.1016/j.apradiso.2015.04.008

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

Appl Radiat Isot. 2015 Aug:102:15-28. doi: 10.1016/j.apradiso.2015.04.008. Epub 2015 Apr 15.

Authors

S M Collins¹, A K Pearce², P H Regan³, J D Keightley²

Affiliations

¹ National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom. Electronic address: smc1@npl.co.uk.
² National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom.
³ National Physical Laboratory, Hampton Road, Teddington, Middlesex TW11 0LW, United Kingdom; Department of Physics, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom.

PMID: 25933406
DOI: 10.1016/j.apradiso.2015.04.008

Abstract

Precise measurements of the absolute γ-ray emission probabilities have been made of radiochemically pure solutions of (223)Ra 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 (223)Ra decay series. Absolute γ-ray emission probabilities and standard uncertainties have been determined for the decay of (223)Ra, (219)Rn, (215)Po, (211)Pb, (211)Bi and (207)Tl 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 (223)Ra, (219)Rn and (211)Pb have been determined and are presented. The α-transition probabilities of the (223)Ra 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.

Keywords: (207)Tl; (211)Pb; (215)Po; (219)Rn; (223)Ra; Correlation coefficients; Gamma-ray emission probabilities; Gamma-ray spectrometry; Nuclear data; Radioactivity.