Observation of the Exotic Isotope F13 Located Four Neutrons beyond the Proton Drip Line

A F13 resonance was observed following a charge-exchange reaction between a fast O13 beam and a Be9 target. The resonance was found in the invariant-mass distribution of 3p+C10 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 O12, which subsequently undergo 2p decay. In addition, there may also be a significant proton decay branch to the second 2+ level in O12. 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 O12.Received 16 November 2020Revised 22 January 2021Accepted 24 February 2021DOI:https://doi.org/10.1103/PhysRevLett.126.132501© 2021 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasCharge-exchange reactionsEnergy levels & level densitiesLifetimes & widthsNuclear structure & decaysProton emissionRare & new isotopesProperties6 ≤ A ≤ 19TechniquesRadioactive beamsNuclear Physics