Novel Penning-trap techniques reveal isomeric states in $^{128}$In and $^{130}$In for the first time

TL;DR

This study employs novel Penning-trap techniques to discover and measure isomeric states in $^{128}$In and $^{130}$In, providing new insights into their nuclear structure and informing shell-model calculations.

Contribution

The paper introduces new ion manipulation methods in Penning traps to identify and measure isomeric states in indium isotopes for the first time.

Findings

Discovery of a new high-spin isomer in $^{128}$In at 1797.6 keV.

First resolution of the $10^-$ isomeric state in $^{130}$In at 58.6 keV.

Measured energy differences between states are lower than shell-model predictions.

Abstract

Isomeric states in $^{128}$In and $^{130}$In have been studied with the JYFLTRAP Penning trap at the IGISOL facility. By employing novel ion manipulation techniques, different states were separated and masses of six beta-decaying states were measured. JYFLTRAP was also used to select the ions of interest for identification at a post-trap decay spectroscopy station. A new beta-decaying high-spin isomer feeding the $15^-$ isomer in $^{128}$Sn has been discovered in $^{128}$In at $1797.6(20)$ keV. Shell-model calculations employing a CD-Bonn potential re-normalized with the perturbative G-matrix approach suggest this new isomer to be a $16^+$ spin-trap isomer. In $^{130}$In, the lowest-lying $(10^-)$ isomeric state at $58.6(82)$ keV was resolved for the first time using the phase-imaging ion cyclotron resonance technique. The energy difference between the $10^-$ and $1^-$ states in $^{130}$In, stemming from parallel/antiparallel coupling of $(\pi 0g_{9/2}^{-1})\otimes(\nu 0h_{11/2}^{-1})$, has been found to be around 200 keV lower than predicted by the shell model. Precise information on the energies of the excited states determined in this work is crucial for producing new improved effective interactions for the nuclear shell model description of nuclei near $^{132}$Sn.