The N=28 shell closure; from N = Z to the neutron drip line

摘要

The evolution of the N = 28 neutron shell closure is studied in the N = 28 isotones from neutron drip line's Mg-40 to N = Z doubly magic Ni-56. It is found that the N = 28 closure vanishes at Z = 12 in favor of a deformed ground state. For Z = 14 and Z = 16 closed shell and intruder configurations are almost degenerate, leading to highly mixed ground states and to very low lying excited 0(+) states. For Z > 20 the intruder states are always above the closed shell ground states. We examine their structure and their possible existence as collective yrare bands of well-defined particle-hole character. (C) 2004 Elsevier B.V. All rights reserved.