Coupling a Proton and a Neutron to the Semidoubly Magic Nucleus Ni-68: A Study of Cu-70 via the Beta Decay of Ni-70 and Cu-70

The 70Ni nucleus has been produced at the LISOL facility and its beta decay to 70Cu has been observed. In parallel, the 70Cu nucleus has been produced at the ISOLDE facility. A new third beta-decaying isomeric state in 70Cu has been identified, partly with the aid of the in-source laser spectroscopy method. Its measured half-life is T1/2=33(2) s. In addition, two isomeric transitions in 70Cu have been observed at energies of 101.1(3) and 141.3(3) keV, and it allowed the relative placement of the three 70Cu isomeric states and their tentative spin and parity assignments. The new 70Cu isomer was found to be weakly populated in the beta decay of 70Ni. It allowed the construction of the 70Ni decay scheme. Furthermore, the beta decay of the three 70Cu isomers to 70Zn has been measured and their decay schemes are presented. The 70Ni beta decay to the isomeric states in 70Cu and their subsequent isomeric decay and beta decay to 70Zn are discussed within the extreme shell-model picture of two valence nucleons outside the semidouble magic ₂₈⁶⁸Ni40 core and it yields satisfactory results. Large-basis shell-model calculations using ₂₈⁵⁶Ni28 as the core and a realistic effective interaction support rather well the suggested interpretation.