Experimental study of the $^{66}$Ni$(d,p)^{67}$Ni one-neutron transfer reaction

The quasi-SU(3) sequence of the positive parity nu g(9/2), d(5/2), s(1/2) orbitals above the N = 40 shell gap are assumed to induce strong quadrupole collectivity in the neutron-rich Fe (Z = 26) and Cr (Z = 24) isotopes below the nickel region. In this paper the position and strength of these single-particle orbitals are characterized in the neighborhood of Ni-68 (Z = 28, N = 40) through the Ni-66(d, p)Ni-67 one-neutron transfer reaction at 2.95 MeV/nucleon in inverse kinematics, performed at the REX-ISOLDE facility in CERN. A combination of the Miniball gamma-array and T-REX particle-detection setup was used and a delayed coincidence technique was employed to investigate the 13.3-mu s isomer at 1007 keV in Ni-67. Excited states up to an excitation energy of 5.8MeV have been populated. Feeding of the nu g(9/2) (1007 keV) and nu d(5/2) (2207 keV and 3277 keV) positive-parity neutron states and negative parity (nu pf) states have been observed at low excitation energy. The extracted relative spectroscopic factors, based on a distorted-wave Born approximation analysis, show that the d(5/2) single-particle strength is mostly split over these two excited states. The results are also compared to the distribution of the proton single-particle strength in the 90Zr region (Z = 40, N = 50).