Nuclear structure beyond the neutron drip line: the lowest energy states in ⁹He via their T=5/2 isobaric analogs in ⁹Li

الأصل · EN

The level structure of the very neutron rich and unbound ⁹He nucleus has been the subject of significant experimental and theoretical study. Many recent works have claimed that the two lowest energy ⁹He states exist with spins Jπ=1/2+ and Jπ=1/2- and widths on the order of hundreds of 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 ⁸He+n system, performed via a search for the T=5/2 isobaric analog states in ⁹Li populated through ⁸He+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 ⁹He located approximately 3 MeV above the neutron decay threshold.