Resolution of a discrepancy in the γ -ray emission probability from the β decay of Ce g 137

We have deduced the emission probability of the 447-keV γ ray from the ɛ+β+ decay of 137Ceg (9.0 h) relative to that of the 254-keV γ ray from the 137Cem (34.4 h) decay in transient equilibrium. The time-dependent factor in transient equilibrium was applied following the Bateman equation for a radioactive decay chain. The isotope was produced via the 139La(p,3n)137Cem,g reaction by bombarding natLa with a proton beam from the 88-in. cyclotron at Lawrence Berkeley National Laboratory. γ-ray intensities were measured using an HPGe detector. The emission probability for the 447-keV γ ray deduced in this work is 1.21(3) (that is 1.21 ± 0.03) per hundred parent decays, which differs significantly from an earlier published value of 2.24(10). We identify the source of this discrepancy to be an incorrect use of the time-dependent factor. Additionally, we have deduced the emission probability of the 504-keV γ ray from the decay of 85Yg (2.68 h) relative to that of the 232-keV γ ray from the 85Srm (1.127 h) decay in transient equilibrium. The isotope was produced via the 86Sr(p,2n)85Yg reaction by bombarding 86SrCO3 with a proton beam at the same facility. The study confirms the assumption of the time-dependent correction for recommending the emission probability of the 504-keV γ ray in the literature. Our work highlights the importance of explicit description by authors of any time-dependent correction they have made when reporting γ-ray intensities for nuclides in transient equilibrium. The need and significance of accurate and precise decay data of 137Ceg and 85Yg in basic science and medicine is briefly outlined.