The unbound nucleus ^{26}O has been investigated using invariant-mass spectroscopy following one-proton removal reaction from a ^{27}F beam at 201  MeV/nucleon. The decay products, ^{24}O and two neutrons, were detected in coincidence using the newly commissioned SAMURAI spectrometer at the RIKEN Radioactive Isotope Beam Factory. The ^{26}O ground-state resonance was found to lie only 18±3(stat)±4(syst)  keV above threshold. In addition, a higher lying level, which is most likely the first 2^{+} state, was observed for the first time at 1.28_{-0.08}^{+0.11}  MeV above threshold. Comparison with theoretical predictions suggests that three-nucleon forces, pf-shell intruder configurations, and the continuum are key elements to understanding the structure of the most neutron-rich oxygen isotopes beyond the drip line.

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The halo structure of 31 Ne is studied using 1n-removal reactions on C and Pb targets at 230 MeV=nucleon. A combined analysis of the cross sections of these nuclear and Coulomb dominated reactions that feed directly the 30 Ne ground-state reveals 31 Ne to have a small neutron separation energy, 0.15 þ0.16 −0.10 MeV, and spin-parity 3=2 − . Consistency of the data with reaction and large-scale shell-model calculations identifies 31 Ne as deformed and having a significant p-wave halo component, suggesting that halos are more frequent occurrences at the neutron drip line.

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