Observation of neutron-unbound resonant states in 23O and 28Ne

The decay energy spectra of neutron-rich 23O and 28Ne were measured. The isotopes were produced in stripping reactions from a 85MeV/u 29Na beam on a beryllium target. Neutrons were measured in coincidence with light neutron-rich fragments produced in stripping reactions from an 85MeV/u 29Na beam on a beryllium target. The neutrons were detected with the Modular Neutron Array (MoNA) and the fragments were analyzed with the MSU/FSU Sweeper magnet system. Low-energy resonances close to the neutron-separation energies were observed in both system. The results for 23O agrees with a previous measurement\footnote{A. Schiller et al., Phys. Rev. Lett. 99 (2007) 112501} and the resonance in 28Ne was observed for the first time.