The level structure of the very neutron rich and unbound 9 He nucleus has been the subject of significant experimental and theoretical study. Many recent works have claimed that the two lowest energy 9 He states exist with spins Jπ=1/2+ and Jπ=1/2− and widths on the order of 100–200 keV. These findings cannot be reconciled with our contemporary understanding of nuclear structure. The present work is the first high-resolution study with low statistical uncertainty of the relevant excitation energy range in the 8 He+n system, performed via a search for the T=5/2 isobaric analog states in 9 Li populated through 8 He+p elastic scattering. The present data show no indication of any narrow structures. Instead, we find evidence for a broad Jπ=1/2+ state in 9 He located approximately 3 MeV above the neutron decay threshold.
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"value": "The level structure of the very neutron rich and unbound 9 He nucleus has been the subject of significant experimental and theoretical study. Many recent works have claimed that the two lowest energy 9 He states exist with spins J\u03c0=1/2+ and J\u03c0=1/2\u2212 and widths on the order of 100\u2013200 keV. These findings cannot be reconciled with our contemporary understanding of nuclear structure. The present work is the first high-resolution study with low statistical uncertainty of the relevant excitation energy range in the 8 He+n system, performed via a search for the T=5/2 isobaric analog states in 9 Li populated through 8 He+p elastic scattering. The present data show no indication of any narrow structures. Instead, we find evidence for a broad J\u03c0=1/2+ state in 9 He located approximately 3 MeV above the neutron decay threshold."
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