Neutron-unbound excited states of 23N

Neutron unbound states in N-23 were populated via proton knockout from an 83.4 MeV/nucleon O-24 beam on a liquid deuterium target. The two-body decay energy displays two peaks at E-1 similar to 100 keV and E-2 similar to 1MeV with respect to the neutron separation energy. The data are consistent with shell model calculations predicting resonances at excitation energies of similar to 3.6MeV and similar to 4.5MeV. The selectivity of the reaction implies that these states correspond to the first and second 3/2(-) states. The energy of the first state is about 1.3 MeV lower than the first excited 2(+) in O-24. This decrease is largely due to coupling with the pi p(3/2)(-1) hole along with a small reduction of the N = 16 shell gap in N-23.