Core-coupled protons, f 7 / 2 intruder states, and competing g 9 / 2 proton and neutron structures in 65 , 67 Cu

The nuclei Cu-65,Cu-67 were studied in reactions between a 430-MeV Ni-64 beam and a thick U-238 target with the Gammasphere array. Decay schemes for both nuclei have been extended, with spin and parity assignments of observed states constrained by measured gamma-ray angular distributions and correlations. Positive-parity level structures, based on p(3/2) protons coupled to negative-parity states in the Ni cores, have been identified above the known 9/2(+) states. In Cu-67, a negative-parity dipole band built upon a pi f(7/2)(-1) state has been observed, as were two shorter negative-parity sequences. A qualitative description of the level structures has been obtained through comparison with systematics of the odd-Lambda Cu57-71 isotopes and with states in the neighboring even-even Ni and Zn cores. Shell-model calculations using JUN45 and jj44b effective interactions were performed for Cu-65,Cu-67, with jj44b providing overall better agreement with the data. Both are limited, however, by the restriction that the f(7/2) and g(9/2) orbitals are not available simultaneously in the basis. Proton f(7/2) and neutron g(9/2) orbitals are required for the full negative-parity spectrum of states, while g(9/2) protons and neutrons are both important for positive-parity levels. The latter states are found to be better described in terms of weak coupling of a proton to the Ni core.