The First 2(+) Excited State Of O-24

The unbound excited states of the most neutron-rich dripline oxygen isotope, O-24 (Z=8, N=16), have been investigated using the O-24(p,p')O-24* reaction at the beam energy of 63 MeV/nucleon in inverse kinematics at RIKEN. The O-24 beam was produced in the projectile-like fragmentation process of a 95 MeV/nucleon Ar-40 primary beam on the Be production target. The decay energy spectrum of O-24* in O-23+n channel was reconstructed in the invariant mass of the neutron and the charged fragment detected in coincidence. The first unbound excited state of O-24 has been observed at E-x=4.68(-0.14)(+0.21) MeV (preliminary) along with the evidence for another higher lying state at around 7.3 MeV. The energy of the former state is compared with existing data and the results of shell-model calculations.