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

The structure of the light exotic nucleus 8He was investigated using direct reactions of the 8He SPIRAL beam on a proton-rich target. The (p,p') scattering to the state, the (p,d)7He and (p,t)6He transfer reactions, were measured at the energy Elab=15.7 A.MeV. The light charged particles (p,d,t) were detected in the MUST Si-strip telescope array. The excitation spectrum of 8He was extracted from the (p,p') reaction. Above the known 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 α+4n models assuming a pure 4(1p3/2) configuration.