Study of the T$=$5/2 states in $^{9}$Li (analogs of the lowest states in $^{9}$He) as a test of nuclear structure theory for drip line nuclei

About 20 years ago, a group of Hahn-Meitner Institute made precision measurements of a multi nucleon transfer reaction to populate the lowest states in $^{9}$He. They found [1,2] a state of $^{9}$He(1/2$^{-})$ at 1.27 $\pm$ 0.10 MeV above the $^{8}$He $+$ n threshold with $\Gamma =$ 0.10 $\pm$ 0.06 MeV. Since then, many groups tried to obtain detailed information on $^{9}$He mainly using rare isotope beams. However, the energy resolution and counting statistics was never sufficient to test the data [1,2] (see a review in [3]). Additionally an MSU group [4] found a virtual s-wave state within 0.2 MeV of the $^{8}$He$+$n threshold which they claimed to be the ground state of $^{9}$He. The theoretical calculations demonstrate rare unanimity. A variety of approaches including the recent [5]\textit{ ab initio} calculations predict a broad state, approximately ten times broader than given in Refs. [1,2]. So it can be that our understanding of nuclear structure at the border of nuclear stability is seriously deficient. To date, it looks like all straightforward ways to obtain spectroscopic information on $^{9}$He were tested. So, we populated T$=$5/2 states in $^{9}$Li (analogs of $^{9}$He) in $^{8}$He$+$p resonance elastic scattering using the TTIK method [5,6]. The measurements were performed using 4 MeV/A $^{8}$He beam provided by TRIUMF facilities. The scattering chamber was filled with CH$_{4}$ gas. The proton recoils were detected by an array of position sensitive proportional counters and silicon detectors. The experimental equipment was tested using 3.5 and 7 MeV/A $^{12}$C beams of Cyclotron Institute at TAMU.