Observation of the Exotic Isotope 13F Located Four Neutrons beyond the Proton Drip Line

A 13F resonance was observed following a charge-exchange reaction between a fast 13O beam and a 9Be target. The resonance was found in the invariant-mass distribution of 3p + 10C events and probably corresponds to a 5/2+ excited state. The ground state was also expected to be populated, but was not resolved from the background. The observed level decays via initial proton emissions to both the ground and first 2+ state of 12O , which subsequently undergo 2p decay. In addition, there may also be a significant proton decay branch to the second 2+ level in 12O . The wave function associated with the observed level may be collectivized due to coupling to the continuum as is it located just above the threshold for proton decay to the 2+2 state of 12O .