Abstract
Excited states in Zn-56 were populated following one-neutron removal from a Zn-57 beam impinging on a Be target at intermediate energies in an experiment conducted at the Radioactive Isotope Beam Factory at RIKEN. Three gamma rays were observed and tentatively assigned to the 6(+) -> 4(+) -> 2(+) -> 0(+) yrast sequence. This turns Zn-56 into the heaviest T-z = -2 nucleus in which excited states are known. The excitation-energy differences between these levels and the isobaric analogue states in the T-z = +2 mirror partner, Fe-56, are compared with large-scale shell-model calculations considering the full pf valence space and various isospin-breaking contributions. This comparison, together with an analysis of the mirror energy differences in the A = 58, T-z = +/- 1 pair Zn-58 and Ni-58, provides valuable information with respect to the size of the monopole radial and the isovector multipole isospin-breaking terms in the region above doubly-magic Ni-56. (C) 2021 The Author(s). Published by Elsevier B.V.