Shell structure in neutron-rich Ca and Ni nuclei under semi-realistic mean fields

Abstract

Shell structure in the neutron-rich Ca and Ni nuclei is investigated by the spherical Hartree-Fock calculations with the semi-realistic $NN$ interactions. Specific ingredients of the effective interaction, particularly the tensor force, often play a key role in the $Z$ dependence of the neutron shell structure. Such examples are found in N=32 and N=40; N=32 becomes magic or submagic in ${}^{52}$Ca while its magicity is broken in ${}^{60}$Ni, and N=40 is submagic (though not magic) in ${}^{68}$Ni but not in ${}^{60}$Ca. Comments are given on the doubly magic nature of ${}^{78}$Ni. We point out that the loose binding can lead to a submagic number N=58 in ${}^{86}$Ni, assisted by the weak pair coupling.

Comments: 14 pages including 5 figures, to appear in Physical Review C (Rapid Communication)