Observation of a broad $p$-wave resonant state in ${}^9$He

Abstract

We report on the two-body invariant-mass spectroscopy of ${}^9$He, populated via the 1$p$1$n$ knockout reaction from the two-neutron halo nucleus ${}^{11}$Li at $\sim$250 MeV/nucleon. A broad $p$-wave resonant state of ${}^9$He was observed at 1.28(1) MeV with a width of 0.82(4) MeV.