Observation of collective modes of excitations in Co 59, Ni 59, and Co 61 and the influence of the g9/2 orbital

High-spin states in Co59 (Z=27), Ni59 (Z=28), and Co61 have been populated by the fusion evaporation reactions, Ti48(C14,p2n)Co59, Ti48(C14,3n)Ni59, and Ti50(C14,p2n)Co61. The 9 MV tandem accelerator at the John D. Fox Laboratory, Florida State University (FSU) was used to accelerate the C14 beam and the deexciting γ rays were detected by the FSU detector array consisting of six high-purity germanium (HPGe) clover detectors and three single crystals. Directional correlation of the γ rays deexciting oriented states (DCO ratios) and polarization asymmetry measurements helped to establish spin and parities of the excited states whenever possible. The level scheme of Co59 has been expanded with the inclusion of positive-parity states up to 31/2+ at around 11 MeV. The Ni59 positive-parity states known from previous study were verified with modifications to some of the spins and parities. On the other hand, the negative-parity states were extended to 31/2 at an excitation energy of 12 MeV. No new transition was observed for Co61, but one of the major bands has been reassigned as consisting of positive-parity states by reason of this study. Excitations observed within the f7/2, p3/2, f5/2, and p1/2 orbitals, and also across the N=40 subshell closure into the g9/2 orbital was established by comparison with large-scale shell-model calculations for the three nuclei studied.