Abstract
The low-lying structure of the neutron-rich nucleus has been investigated at the Radioactive Isotope Beam Factory using in-beam -ray spectroscopy with , , and multinucleon removal reactions at . A -ray peak at 1178(18) keV is reported and assigned as the transition from the first state to the ground state. A weaker, tentative line at 1582(38) keV is suggested as the transition. The experimental results are compared to large-scale shell-model calculations performed in the model space using the SDPF-MU effective interaction with modifications based on recent experimental data for exotic calcium and potassium isotopes. The modified Hamiltonian provides a satisfactory description of the new experimental results for and, more generally, reproduces the energy systematics of low-lying states in neutron-rich Ar isotopes rather well. The shell-model calculations indicate that the subshell gap in is similar in magnitude to those in and and, notably, predict an subshell closure in that is larger than the one recently reported in .
- Received 20 April 2015
DOI:https://doi.org/10.1103/PhysRevLett.114.252501
© 2015 American Physical Society