# Masses of ground and isomeric states of $^{101}$In and configuration-dependent shell evolution in odd-$A$ indium isotopes

## TL;DR

This paper presents precise mass measurements of ground and isomeric states in $^{101}$In, revealing configuration-dependent shell evolution and confirming a smooth trend in excitation energies near the $N=50$ magic number, with implications for nuclear structure models.

## Contribution

It introduces the concept of configuration-dependent shell evolution (type II) in odd-$A$ nuclei and demonstrates the importance of neutron configuration mixing in shell model calculations.

## Key findings

- Isomeric excitation energy follows a smooth trend up to $N=50$.
- Single particle energies vary for different states within the same isotope.
- Shell model calculations require neutron configuration mixing for accuracy.

## Abstract

We report first precision mass measurements of the $1/2^-$ isomeric and $9/2^+$ ground states of $^{101}$In. The determined isomeric excitation energy continues a smooth trend of odd-$A$ indium isotopes up to the immediate vicinity of $N=50$ magic number. This trend can be confirmed by dedicated shell model calculations only if the neutron configuration mixing is considered. We find that the single particle energies are different for different states of the same isotope. The presented configuration-dependent shell evolution, type II shell evolution, in odd-$A$ nuclei is discussed for the first time. Our results will facilitate future studies of single-particle neutron states.