Neutron unbound states in 19,21C have been populated by nucleon removal from a beam of 22N at 68 MeV/u, and the invariant mass method was used to reconstruct decay energies of the reaction products. Charged fragments were bent from the beam axis by a dipole magnet and their properties measured by a suite of charged particle detectors sufficient to identify individual reaction products and reconstruct momentum vectors at the reaction target. Neutrons were detected at forward angles by the Modular Neutron Array (MoNA), which measured their trajectory and time of flight.A resonance at 76±14 keV was observed in the decay spectrum of 19C, corresponding to an excited state at 383±15 keV. Comparison to shell model calculations results in the assignment of this state to the 5/21+ state in 19C, and the resulting level scheme indicates a breakdown in existing shell model descriptions of this nucleus. In the case of 21C, an s-wave line shape was used to describe the experimental decay energy spectrum, resulting in a scattering length limit of |a_s| < 1.5 fm. This result suggests that 22C is bound by less than 100 keV.
Read
