Particle-core coupling around 68Ni:: a study of the subshell closure at N=40

The existence of a subshell gap at neutron number N = 40 is investigated in the odd-mass Ni and Cu isotopes using the Particle-Core Coupling Model (PCM), The calculated properties are in good agreement with the existing experimental data. suggesting that Ni-68 is a good core for the adjacent nuclei. Evaluation of the 2(1)(+) excitation energies, two-neutron separation energies, and pairing properties of the Ni isotopes reveals discontinuities at neutron number N = 40, These data support the existence of a significant neutron subshell gap at N = 40, for Z = 28, The systematic behavior of the proton single-particle energies extracted from the particle-con coupling calculations for the odd-mass Cu isotopes is discussed in terms of monopole shifts. The effect is consistent with the existence of a neutron subshell gap at N = 40, (C) 2000 Elsevier Science B.V. All rights reserved.