Absence of Low-Energy Shape Coexistence in $^{80}$Ge: The Nonobservation of a Proposed Excited 0$_2^+$ Level at 639 keV

TL;DR

This study used high-precision gamma and beta spectroscopy to investigate the structure of $^{80}$Ge, finding no evidence for a previously proposed low-energy excited 0+ state, thus challenging the shape coexistence hypothesis.

Contribution

The paper provides the first high-statistics experimental search for the 0+2 state in $^{80}$Ge, combined with shell model calculations, to conclusively show its absence at low energy.

Findings

No evidence for the 639-keV 0+2 level in $^{80}$Ge.

Shell model predicts the 0+2 state at around 2 MeV.

Low-energy shape coexistence is unlikely in $^{80}$Ge.

Abstract

The $^{80}$Ge structure was investigated in a high-statistics $\beta$-decay experiment of $^{80}$Ga using the GRIFFIN spectrometer at TRIUMF-ISAC through $\gamma$, $\beta$-$e$, $e$-$\gamma$ and $\gamma$-$\gamma$ spectroscopy. No evidence was found for the recently reported 0$_2^{+}$ 639-keV level suggested as evidence for low-energy shape coexistence in $^{80}$Ge. Large-scale shell model calculations performed in $^{78,80,82}$Ge place the $0^{+}_{2}$ level in $^{80}$Ge at 2\,MeV. The new experimental evidence combined with shell model predictions indicate that low-energy shape coexistence is not present in $^{80}$Ge.