Evidence for aβ-decaying1/2−isomer inNi71

Abstract

We report on the investigation of the population mechanism for the 454-keV level in 71 Cu. This level was identified for the first time in a recent Coulomb excitation measurement with a radioactive beam of 71 Cu. The selective nature of the Coulomb-excitation process as well as nuclear-structure considerations constrain the possible spin values for the newly observed state to I π = 1/2 ― . A reexamination of the data set obtained in a β-decay study at the Leuven isotope separator on-line mass separator (LISOL) revealed that this state is also populated in the decay of 71 Ni, most probably by direct feeding from a newly identified 1/2 ― β-decaying isomer having a T 1/2 = 2.3(3) s. In this paper, we investigate the proposed scenario by reanalyzing the β-γ and γ-γ coincidences obtained in the β-decay study at LISOL.