Low-spin states in Ge-80 populated in the beta decay of the Ga-80 3(-) isomer

Abstract

The structure of Ge-80 has been investigated at the ISOLDE facility at CERN. A previous study reported for the first time a low-lying 0(2)(+) intruder state at 639 keV, based on the coincidence with a previously unobserved 1764-keV gamma ray, and suggested it as evidence for shape coexistence in Ge-80. We used the beta decay from the 3(-) 22.4-keV state in Ga-80 to enhance the population of low-spin states in Ge-80, including any excited 0(+) level, and gamma gamma coincidences to investigate it. We observed a 1764-keV gamma ray in coincidence with strong transitions in Ge-80, thus not feeding the proposed 639-keV 0(2)(+). No connecting transitions from previously known levels to the 639-keV and 2403-keV 2(3)(+) 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 0(2)(+) state below approximate to 1200 keV in Ge-80. Our experimental findings and shell-model calculations are difficult to reconcile with a very low-lying 0(2)(+) state in Ge-80.