Invariant-mass spectrum of O11

The invariant-mass distribution of O-11 fragments formed in two-neutron-knockout reactions with a O-13 projectile and Be-9 target has been further examined. Gating on events where the C-9 decay fragments produced following 2p emission are recoiled transversely in the projectile's frame improves the overall invariant-mass resolution. The observed peak is now shown to have contributions from at least two O-11 levels, in contradiction with the suggestion of Fortune [Phys. Rev. C 99, 051302(R) (2019)]. The data, however, do not differentiate between the ground-state properties obtained by the Gamow coupled-channels calculation and the prompt 2p-decay model of Fortune. The ground-state 2p-decay energy is 4.25(6) MeV in a two-level fit to the data, but lower values are possible if more states contribute to the observed spectrum, as suggested in the previous analysis.