Study of unbound excited states in 50,52 Ar and the shell closures at N = 32 and N = 34

Neutron-unbound states in 50 Ar and 52 Ar were investigated via the (p,2p) proton-knockout reaction using the invariant-mass spectroscopy technique. Two ( 50 Ar) and three ( 52 Ar) distinct, narrow resonances were observed in the vicinity of the neutron separation energy. Based on a comparison with theoretical level schemes and calculated (p,2p) cross sections, tentative spin-parity assignments have been proposed. The good degree of consistency between the predicted level structures and the observed states indicates that the large N = 32 and N = 34 shell gaps inherent in the theoretical calculations accurately describe the nuclear structure in this region. These results provide further support for the robustness of these subshell closures in the neutron-rich argon isotopes.