Spectroscopic study of $^{47}$Ca from the $\beta^-$ decay of $^{47}$K

TL;DR

This study provides a detailed spectroscopic analysis of the beta decay of potassium-47 to calcium-47, revealing new transitions, more precise half-life, and new state assignments, thereby improving understanding of nuclear structure in this region.

Contribution

The paper presents the first high-resolution, high-efficiency measurement of $^{47}$K beta decay, discovering 48 new transitions and refining nuclear level schemes and decay properties.

Findings

48 new transitions observed in $^{47}$Ca

Refined half-life of $^{47}$K to 17.38(3) seconds

Identification of beta-feeding to high-lying states between 4.5 and 6.1 MeV

Abstract

The $\beta^-$ decay of $^{47}$K to $^{47}$Ca is an appropriate mechanism for benchmarking interactions spanning the $sd$ and $pf$ shells, but current knowledge of the $\beta^-$-decay scheme is limited. We have performed a high-resolution, high-efficiency study of the $\beta^-$-decay of $^{47}$K with the GRIFFIN spectrometer at TRIUMF-ISAC. The study revealed 48 new transitions, a more precise value for the $^{47}$K half-life (17.38(3)~s), and new spin and parity assignments for eight excited states. Levels placed for the first time here raise the highest state observed in $\beta^-$ decay to within 568(3) keV of the $Q$-value and confirm the previously measured large $\beta^-$-decay branching ratios to the low-lying states. Previously unobserved $\beta^-$-feeding to 3/2$^+$ states between 4.5 and 6.1~MeV excitation energy was identified with a total $\beta^-$-feeding intensity of 1.29(2)\%. The sum of the $B(GT)$ values for these states indicates that the $1s_{1/2}$ proton hole strength near this excitation energy is comparable to the previously known $1s_{1/2}$ proton and neutron hole strengths near 2.6 MeV.