Low-spin states in Ge80 populated in the β decay of the Ga80

The structure of Ge80 has been investigated at the ISOLDE facility at CERN. A previous study reported for the first time a low-lying 02+ intruder state at 639 keV, based on the coincidence with a previously unobserved 1764-keV γ ray, and suggested it as evidence for shape coexistence in Ge80. We used the β decay from the 3− 22.4-keV state in Ga80 to enhance the population of low-spin states in Ge80, including any excited 0+ level, and γγ coincidences to investigate it. We observed a 1764-keV γ ray in coincidence with strong transitions in Ge80, thus not feeding the proposed 639-keV 02+. No connecting transitions from previously known levels to the 639-keV and 2403-keV 23+ states could be established either. Shell-model calculations for Ge isotopes and N=48 isotones were performed. They succeed to explain most of the experimental levels, but fail to reproduce the presence of a 02+ state below ≈1200 keV in Ge80. Our experimental findings and shell-model calculations are difficult to reconcile with a very low-lying 02+ state in Ge80.1 MoreReceived 20 October 2020Revised 23 July 2021Accepted 27 July 2021DOI:https://doi.org/10.1103/PhysRevC.104.024317Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasIsomer decaysNuclear structure & decaysProperties59 ≤ A ≤ 89TechniquesRadiation detectorsRadioactive beamsSpectrometers & spectroscopic techniquesNuclear Physics