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 3 p + 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 2 p 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 2₂⁺ state of ¹²O.