First ${\beta}$-decay spectroscopy of $^{135}$In and new ${\beta}$-decay branches of $^{134}$In

TL;DR

This study presents the first detailed beta-decay spectroscopy of $^{134}$In and $^{135}$In, revealing new decay branches, excited states, and decay properties that enhance understanding of neutron-rich tin isotopes near the $N=82$ shell closure.

Contribution

It provides the first observation of beta decay branches and excited states in $^{134}$In and $^{135}$In, including new gamma-ray transitions and level schemes, with experimental data compared to shell-model predictions.

Findings

Three beta-decay branches of $^{134}$In were established, two observed for the first time.

Six new levels in $^{134}$Sn were identified from beta-gamma coincidences.

Beta-delayed one-neutron decay of $^{134}$In is dominant despite the Gamow-Teller resonance location.

Abstract

The $\beta$ decay of the neutron-rich $^{134}$In and $^{135}$In was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number $Z=50$ above the $N=82$ shell. The $\beta$-delayed $\gamma$-ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three $\beta$-decay branches of $^{134}$In were established, two of which were observed for the first time. Population of neutron-unbound states decaying via $\gamma$ rays was identified in the two daughter nuclei of $^{134}$In, $^{134}$Sn and $^{133}$Sn, at excitation energies exceeding the neutron separation energy by 1 MeV. The $\beta$-delayed one- and two-neutron emission branching ratios of $^{134}$In were determined and compared with theoretical calculations. The $\beta$-delayed one-neutron decay was observed to be dominant $\beta$-decay branch of $^{134}$In even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of $^{134}$Sn. Transitions following the $\beta$ decay of $^{135}$In are reported for the first time, including $\gamma$ rays tentatively attributed to $^{135}$Sn. In total, six new levels were identified in $^{134}$Sn on the basis of the $\beta \gamma \gamma$ coincidences observed in the $^{134}$In and $^{135}$In $\beta$ decays. A transition that might be a candidate for deexciting the missing neutron single-particle $13/2^+$ state in $^{133}$Sn was observed in both $\beta$ decays and its assignment is discussed. Experimental level schemes of $^{134}$Sn and $^{135}$Sn are compared with shell-model predictions. Using the fast timing technique, half-lives of the $2^+$, $4^+$ and $6^+$ levels in $^{134}$Sn were determined.