Study of the deformation-drivingνd5/2orbital in 67 28 Ni 39 using one-neutron transfer reactions

Abstract

The νg 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 68 Ni. Especially the single-particle energies and strengths of these orbitals are of importance. We studied such properties in the nearby 67 Ni 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 γ -detection array and a newly-developed delayed-correlation technique as to investigate μs-isomers. Angular distributions of the ground state and multiple excited states in 67 Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial νg 9/2 (1007 keV) and νd 5/2 (2207 keV and 3277 keV) singleparticle strengths up to an excitation energy of 5.8 MeV. 50% of the νd 5/2 single-particle strength relative to the νg 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 ( 3 He, d) studies in the region around 90 40 Zr 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.

Nucleon transfer reactions with radioactive beams

“…It is therefore of great interest to locate both the proton and neutron single-particle strength in the region around 68 Ni. A first experiment has been performed at REX-ISOLDE at CERN to study the d( 66 Ni, p) 67 Ni reaction [116,152]. With such heavy beams, and in particular the very low beam energy used in this experiment, causing a low resolution for the excitation energy, the detection of coincident γ-rays is a requirement (see figure 15).…”

Experimental study of theNi66(d,p) Ni67Diriken1, Raabe2, Eberth3 et al. 2015Phys. Rev. CSelf Cite9150View full textAdd to dashboardCite

“…1 in Ref. [38] for the 313-keV transition (left and right background next to the 313-keV transition is subtracted) and shows the definition of the delayed and random-delayed windows, which are both 40-μs long. The delayed-coincidence time window hence accounts for 87.5% of the isomeric transitions.…”

Isomeric states in neutron-rich nuclei near N=40

“…Above N = 50, the s and d orbitals also contribute. In 67 Ni, at N = 39, a 9/2 + isomer at 1007 keV [1] originates from the promotion of a particle above the N = 40 harmonic-oscillator shell closure occupying the ν1g 9/2 orbital [2]. Systematic investigations of isomeric states at and beyond N = 40 [3] found many more cases arising from one-or two-particle configurations in the ν1g 9/2 orbital.…”