Evidence for the Ground-State Resonance of 26O

Evidence for the ground state of the neutron-unbound nucleus O-26 was observed for the first time in the single proton-knockout reaction from a 82 MeV/u F-27 beam. Neutrons were measured in coincidence with O-24 fragments. O-26 was determined to be unbound by 150(-150)(+50) keV from the observation of low-energy neutrons. This result agrees with recent shell-model calculations based on microscopic two- and three-nucleon forces.