High-spin spectroscopy in $^{207}$At: Evidence of a 29/2$^{+}$ isomeric state

TL;DR

This paper reports the discovery of a new 29/2$^{+}$ isomeric state in $^{207}$At, extending the level scheme, measuring its half-life, and comparing experimental data with shell-model calculations for better understanding of its nuclear structure.

Contribution

The study provides the first evidence of a 29/2$^{+}$ isomer in $^{207}$At and compares experimental results with advanced shell-model calculations, expanding knowledge of high-spin states in this isotope.

Findings

Extended level scheme up to 47/2$ abla$ and 6.5 MeV

Measured half-life of 25/2$^{+}$ isomer as 107.5(9) ns

Estimated half-life of 29/2$^{+}$ isomer as 2-4.5 μs

Abstract

Yrast and near-yrast states above the known 25/2$^{+}$ isomer in $^{207}$At are established for the first time. The level scheme is extended up to 47/2$\hbar$ and 6.5 MeV with the addition of about 60 new $\gamma$-ray transitions. The half-life of the 25/2$^{+}$ isomer is revisited and a value of $T_{1/2}$ = 107.5(9) ns is deduced. Evidence of a hitherto unobserved 29/2$^{+}$ isomer in $^{207}$At is presented. A systematic study of $B(E3)$ values for the transitions de-exciting the 29/2$^{+}$ isomer in the neighboring odd-$A$ At isotopes suggests a half-life in the 2$-$4.5 $\mu$s range for this state in $^{207}$At. The experimental results are compared with large-scale shell-model calculations performed using the KHM3Y effective interaction in the $Z$ = 50$-$126, $N$ = 82$-$184 model space and an overall good agreement is noted between the theory and the experiment. A qualitative comparison of the excited states and the isomers with analogous states in neighboring nuclei provides further insight into the structure of $^{207}$At.