  The first excited state in neutron-rich 23O was observed in a (2p1n)
knock-out reaction from 26Ne on a beryllium target at a beam energy of 86
MeV/A. The state is unbound with respect to neutron emission and was
reconstructed from the invariant mass from the 22O fragment and the neutron. It
is unbound by 45(2) keV corresponding to an excitation energy of 2.8(1) MeV.
The non-observation of further resonances implies a predominantly direct
reaction mechanism of the employed three-nucleon-removal reaction which
suggests the assignment of the observed resonance to be the 5/2+ hole state.
