β-decay properties of 72 Ni and 72 Cu

The β-decay properties of 72 28Ni44 and 72 29Cu43 have been studied at the LISOL facility of Louvain-La-Neuve and at the CERN-ISOLDE facility, respectively. These neutron-rich nuclei have been produced in the proton-induced fission of 238U. Their decay schemes are presented and the lifetime T1/2 = 6.63(3) s of 72Cu was measured. No β-decaying isomeric state was found in 72Cu, in line with a suggested spin (2) for its ground state. Spin and parity assignments of the observed excited states in the odd-odd nucleus 72Cu are proposed and discussed in terms of coupling between the valence proton and neutrons. Comparison is made with a schematic shell-model picture of 72Cu and with large-scale shell-model calculations performed in the (2p3/21f5/22p1/21g9/2) shell space outside the doubly magic 56 28Ni28 core.