Direct mass measurements of neutron-rich ⁸⁶ Kr projectile fragments and the persistence of neutron magic number <i>N</i> =32 in Sc isotopes

Abstract

In this paper, we present direct mass measurements of neutron-rich $^{86}$Kr\nprojectile fragments conducted at the HIRFL-CSR facility in Lanzhou by\nemploying the Isochronous Mass Spectrometry (IMS) method. The new mass excesses\nof $^{52-54}$Sc nuclides are determined to be -40492(82), -38928(114),\n-34654(540) keV, which show a significant increase of binding energy compared\nto the reported ones in the Atomic Mass Evaluation 2012 (AME12). In particular,\n$^{53}$Sc and $^{54}$Sc are more bound by 0.8 MeV and 1.0 MeV, respectively.\nThe behavior of the two neutron separation energy with neutron numbers\nindicates a strong sub-shell closure at neutron number $N$ = 32 in Sc isotopes.\n