Abstract
High-precision mass measurements of neutron-rich Mn and Fe isotopes are reported. The new mass surface shows no shell closure at . In contrast, there is an increase of the two-neutron separation energy at . This behavior is consistent with the onset of collectivity due to the occupation of intruder states from higher orbits, in analogy with the well known “island of inversion” around . Our results indicate that the neutron-rich Mn isotopes, starting from Mn, are most likely within the new island of inversion. From the new mass surface, we evaluate the empirical proton-neutron interaction and the pairing gap, both playing a significant role in the structural changes in this region.
- Received 29 October 2011
DOI:https://doi.org/10.1103/PhysRevC.86.014325
©2012 American Physical Society