Investigation of the ground-state spin inversion in the neutron-rich Cl-47,Cl-49 isotopes

A first gamma-ray study of Cl-47,Cl-49 spectroscopy was performed at the Radioactive Isotope Beam Factory with 50 Ar projectiles at 217 MeV/nucleon, impinging on the liquid hydrogen target of the MINOS device. Prompt deexcitation gamma rays were measured with the NaI(T1) array DALI2(+). Through the one-proton knockout reaction Ar-50(p, 2p), a spin assignment could be determined for the low-lying states of Cl-49 from the momentum distribution obtained with the SAMURAI spectrometer. A spin-parity J(pi) = 3/2(+) is deduced for the ground state of Cl-49, similar to the recently studied N = 32 isotope K-51. The evolution of the energy difference E(1/2(1)(+)) - E (3/2(1)(+)) is compared to state-of-the-art theoretical predictions.