Low-lying states and structure of the exotic 8He via direct reactions on the proton

The structure of the light exotic nucleus He-8 was investigated using direct reactions of the He-8 SPIRAL beam on a proton-rich target. The (p,p') scattering to the 2(1)(+) state, the (p,d)He-7 and (p,t)He-6 transfer reactions, were measured at the energy El,,(lab) = 15.7 A.MeV. The light charged particles (p,d,t) were detected in the MUST Si-strip telescope array. The excitation spectrum of He-8 was extracted from the (p,p') reaction. Above the known 2(1)(+) excited state at 3.6 MeV, a second resonance was found around 5.4 MeV. The cross sections were analyzed within the coupled-reaction channels framework, using microscopic potentials. It is inferred that the 8He ground state has a more complex neutron-skin structure than suggested by previous a + 4n models assuming a pure (1p(3/2))(4) configuration.