Coupling a proton and a neutron to the semidoubly magic nucleus

The 70Ni nucleus has been produced at the LISOL facility and its b decay to 70Cu has been observed. In parallel, the 70Cu nucleus has been produced at the ISOLDE facility. A new third b-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=33s2d s. In addition, two isomeric transitions in 70Cu have been observed at energies of 101.1(3) and 141.3s3d 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 b decay of 70Ni. It allowed the construction of the 70Ni decay scheme. Furthermore, the b decay of the three 70Cu isomers to 70Zn has been measured and their decay schemes are presented. The 70Ni b decay to the isomeric states in 70Cu and their subsequent isomeric decay and b decay to 70Zn are discussed within the extreme shell-model picture of two valence nucleons outside the semidouble magic 28 Ni40 core and it yields satisfactory results. Large-basis shell-model calculations using 28 Ni28 as the core and a realistic effective interaction support rather well the suggested interpretation.