Levels above the 19/2{sup -} isomer in {sup 71}Cu: Persistence of the N=40 neutron shell gap

Two prompt {gamma} rays of energies 2020 and 554 keV were observed in coincidence with delayed transitions depopulating the 19/2{sup -} isomer in the Z = 29, N = 42 {sup 71}Cu nucleus. The newly identified transitions are proposed to deexcite the 4776- and 5330-keV levels above the 19/2{sup -} isomer. Based on the comparison with the low-lying positive-parity states observed in the Z=42, N=50 {sup 92}Mo nucleus, spin and parity 23/2{sup -} are proposed for the 4776-keV level in {sup 71}Cu. The high-energy, 2020-keV transition is interpreted as arising from the breaking of the N=40 neutron core. Shell-model calculations with a {sup 56}Ni core reproduce the (23/2{sup -}) {yields} (19/2{sup -}) gap well, suggesting that the 23/2{sup -} state is dominated by {pi}p{sub 3/2}{nu}((f{sub p}){sup 10}(g{sub 9/2}){sup 4}) configurations. The present result constitutes further evidence supporting the view that the N=40 subshell closure persists in {sup 71}Cu, herewith challenging recent suggestions that the coupling of two or more proton or neutron quasiparticles induces a large polarization of the {sup 68}Ni core.