Branching Ratios for the Three Most Intense Gamma Rays in the Decay of $^{47}$Ca

TL;DR

This study precisely measured gamma-ray branching ratios in the decay of $^{47}$Ca, improving the accuracy of decay pathways and related beta decay branching ratios through experimental methods and verification techniques.

Contribution

The paper provides significantly more precise gamma-ray branching ratios for $^{47}$Ca decay, refining the understanding of its decay scheme and beta decay branching ratios.

Findings

Gamma-ray branching ratios for $^{47}$Ca decay are now known with greater precision.

The beta decay branching ratios of $^{47}$Ca to $^{47}$Sc states have been indirectly measured.

Half-lives of $^{47}$Ca and $^{47}$Sc were independently verified.

Abstract

A sample of $^{47}$Ca produced through isotope harvesting at the National Superconducting Cyclotron Laboratory was used to measure branching ratios of 7.17(5)%, 7.11(5)%, and 75.0(5)% for the 489.2, 807.9, and 1297.1 keV characteristic gamma-rays, respectively. Based on these updated branching ratios, the ground state to ground state $^{47}$Ca to $^{47}$Sc beta decay branching ratio has been indirectly measured as 17.7(5)% and the ground state to 1297.1 keV excited state as 82.2(5)%. These values represent a greatly increased precision for all five branching ratios compared to the currently accepted values. The measurements presented here were made relative to the ingrown $^{47}$Sc daughter in a $^{47}$Ca sample and the well-established 159.4 keV gamma-ray branching ratio and the half-life for the decay of $^{47}$Sc. These measurements were supported by verifying that the half-lives measured from characteristic gamma-ray peaks over multiple spectra for both $^{47}$Ca and $^{47}$Sc were consistent with previously reported values. Additionally, the half-lives of both $^{47}$Ca and $^{47}$Sc were independently measured with Liquid Scintillation Counting to reverify the previously reported values used in this study to find updated gamma-ray branching ratio values.