DREB Conference 2024

Nuclear resonant states far from the stability line provide a stringent test of nuclear forces at extreme isospin asymmetry. In this talk, I will report on the low-lying resonant states of extremely neutron-rich $^{9}$He and $^{10}$He populated via the (p, 2p) reaction from the 2n-halo nucleus $^{11}$Li at ~250 MeV/nucleon. The obtained $^{9}$He spectrum shows a clear peak at 1.2 MeV with a width of ~ 1 MeV, which is probably a p-wave resonance. The resonance parameters play a key role to understand the $^{8}$He-neutron interactions. The $^{10}$He spectrum was obtained from the three-body invariant mass of $^{8}$He+2n, with much higher statistics than previous measurements [1,2]. The spectrum was compared to the theoretical calculation that combines the coupled-channel three-body model of ${11}$Li [3] and the quasi-free knockout (p, 2p) reaction model [4,5]. Two low-lying 0$^{+}$ resonant states of $^{10}$He were identified at ~ 1 MeV and at ~2 MeV, which have a [s$_{1/2}$ s$_{1/2}$]0$^{+}$ configuration and a [p$_{1/2}$ p$_{1/2}$]0$^{+}$ configuration, respectively.

[1] A. A. Korsheninnikov et al., Phys. Lett. B 326, 31 (1994).
[2] H. T. Johansson et al., Nucl. Phys. A842, 15 (2010).
[3] Y. Kikuchi et al., Phys. Rev. C 87, 034606 (2013).
[4] Y. Kikuchi et al., Prog. Theo. and Expt. Phys, 2016 (2016).
[5] Y. Kubota et al., Phys. Rev. Lett. 125, 252501 (2020).