A Variety Of Particle Alignments In N ≈ N Nuclei

摘要

We study the structure of the N ≈ Z nuclei around A ~ 64 using the shell model with an extended P + QQ Hamiltonian in the configuration space (p_/2, f_5/2, p_1/2, g_9/2). This framework provides a consistent and good description of energy levels, moments of inertia and Q moments in Ge isotopes. We investigate particle alignments in even-even nuclei 64–70Ge, 60–68Zn, and 68Se, in odd-odd N = Z nuclei 62Ga and 66As, and in odd-mass nuclei ~67As and ~69As. It is shown that in these N ≈ Z nuclei structure changes in sequences of the positive- and negative-parity states are caused by various types of particle alignments in the g9/2 orbit. Interestingly enough, one-proton-one-neutron (1p1n) alignment takes place not only in odd-odd N = Z nuclei but also both in even-even nuclei and odd-mass nuclei. A similar mechanism causes competing occupations of a proton and a neutron in the g9/2 orbit, in odd-proton nuclei 67As and 69As.