Measurement of ⁹He ground and excited states

The low-lying structure of exotic nuclide ⁹He is still a subject of experimental and theoretical debate. Experiments have not yet been able to provide a consistent picture of the existence of resonances, nor their spin and parity assignments. An extreme independent particle shell model approach suggests that the ground state of ⁹He resembles a ⁸He core coupled to a valence neutron in the 0p_1/2 shell model orbital, leaning to a total spin and parity of (1/2)^-. However systematics along the N = 7 isotone, and certain theoretical calculations suggest that there may be parity inversion in the ground state of ⁹He, implying that the total spin and parity would be (1/2)⁺. A recent experiment at the NSCL populated low-lying ⁹He resonant states using two different beams and knockout reactions (¹¹Be(-2p) and ¹²B(-3p)) in order to simultaneously constrain both the 0p_1/2 and 1s_1/2 valence neutron orbitals. Preliminary results of the analysis will be presented.