Study of the deformation-driving nu d(5/2) orbital in Ni-67(28)39 using one-neutron transfer reactions
The nu g(9/2), d(5/2), s(1/2) orbitals are assumed to be responsible for the swift onset of collectivity observed in the region below Ni-68. Especially the single-particle energies and strengths of these orbitals are of importance. We studied such properties in the nearby Ni-67 nucleus, by performing a (d, p)-experiment in inverse kinematics employing a post-accelerated radioactive ion beam (RIB) at the REX-ISOLDE facility. The experiment was performed at an energy of 2.95 MeV/u using a combination of the T-REX particle detectors, the Miniball gamma-detection array and a newly-developed delayed-correlation technique as to investigate mu s-isomers. Angular distributions of the ground state and multiple excited states in 67Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial nu g(9/2) (1007keV) and nu d(5/2) (2207 keV and 3277 keV) single-particle strengths up to an excitation energy of 5.8 MeV. 50% of the nu d(5/2) single-particle strength relative to the nu g(9/2)-orbital is concentrated in and shared between the first two observed 5/2(+) levels. A comparison with extended Shell Model calculations and equivalent (He-3, d) studies in the region around Zr-90(40)50 highlights similarities for the strength of the negative-parity pf and positive-parity g(9/2) state, but differences are observed for the d(5/2) single-particle strength. (C) 2014 The Authors. Published by Elsevier B.V.