β-decay properties ofNi72andCu72

Abstract

The \ensuremath{\beta}-decay properties of ${}_{28}^{72}{\mathrm{Ni}}_{44}$ and ${}_{29}^{72}{\mathrm{Cu}}_{43}$ 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 $^{238}\mathrm{U}$. Their decay schemes are presented and the lifetime ${T}_{1/2}=6.63(3)$ s of $^{72}\mathrm{Cu}$ was measured. No \ensuremath{\beta}-decaying isomeric state was found in $^{72}\mathrm{Cu}$, 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 $^{72}\mathrm{Cu}$ are proposed and discussed in terms of coupling between the valence proton and neutrons. Comparison is made with a schematic shell-model picture of $^{72}\mathrm{Cu}$ and with large-scale shell-model calculations performed in the ($2{p}_{3/2}1{f}_{5/2}2{p}_{1/2}1{g}_{9/2}$) shell space outside the doubly magic ${}_{28}^{56}{\mathrm{Ni}}_{28}$ core.