Abstract
The low-lying structure of has been investigated using in-beam -ray spectroscopy with the one-proton removal and inelastic-scattering reactions at the RIKEN Radioactive Isotope Beam Factory. Transitions with energies of 572(4), 695(5), 1539(10), 1730(20), 1854(27), 2091(19), 2452(26), and 3241(39) keV are reported, and a level scheme has been constructed using coincidence relationships and -ray relative intensities. The results are compared to large-scale shell-model calculations in the model space, which account for positive-parity states from proton-hole cross-shell excitations, and to ab initio shell-model calculations from the in-medium similarity renormalization group that includes three-nucleon forces explicitly. The results of proton-removal reaction theory with the eikonal model approach were adopted to aid identification of positive-parity states in the level scheme; experimental counterparts of theoretical and states are suggested from measured decay patterns. The energy of the first state, which is sensitive to the neutron shell gap at the Fermi surface, was determined. The result indicates a rapid weakening of the subshell closure in -shell nuclei at , even when only a single proton occupies the orbital.
- Received 4 August 2017
- Revised 22 September 2017
DOI:https://doi.org/10.1103/PhysRevC.96.064310
©2017 American Physical Society