Unbound excited states of the N=16 closed shell nucleus O-24

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We would like to thank the operations staff at NSCL for providing the primary 48Ca and secondary 26F beams for this experiment. W.F.R. would like to thank B.A. Brown for helpful conversations. This work is supported by NSF Grants No. PHY-0922335, No. PHY-0922409, No. PHY-0922446, No. PHY-0922462, No. PHY-0922473, No. PHY-0922537, No. PHY-0922559, No. PHY-0922622, No. PHY-0922794, No. PHY-0969173, No. PHY-1101745, No. PHY-1205357, and No. PHY-1205537. This work is also based on work supported by the NNSA under Award No. DE-NA0000979.


Two low-lying neutron-unbound excited states of O-24, populated by proton-knockout reactions on F-26, have been measured using the MoNA and LISA arrays in combination with the Sweeper Magnet at the Coupled Cyclotron Facility at the NSCL using invariant mass spectroscopy. The current measurement confirms the separate identity of two states with decay energies 0.51(5) MeV and 1.20(7) MeV, and provides support for theoretical model calculations, which predict a 2(+) first excited state and a 1(+) higher-energy state. The measured excitation energies for these states, 4.70(15) MeV for the 2(+) level and 5.39(16) MeV for the 1(+) level, are consistent with previous lower-resolution measurements, and are compared with five recent model predictions.