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

Abstract

The structure of the light exotic nucleus 8 He was investigated using direct reactions of the 8 He SPIRAL beam on a proton-rich target. The (p,p') scattering to the 2 + 1 state, the (p,d)7 He and (p,t) 6 He transfer reactions, were measured at the energy E 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 8 He 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 8 He ground state has a more complex neutron-skin structure than suggested by previous α + 4n models assuming a pure (1p 3/2 ) 4 configuration.

Role of the tensor interaction in He isotopes with a tensor-optimized shell model

“…For the structures of He isotopes, many experiments have been reported in the neutron-rich side [25][26][27]. However, there are still contradictions in the observed energy levels and their spin assignments.…”

Five-body resonances of8C using the complex scaling method

“…This multiparticle decay condition makes difficulty to identify the states of 8 The mirror nucleus of 8 C is 8 He with isospin T = 2, which has the bound ground state. Recently, many experiments on 8 He have been reported [7][8][9][10][11][12][13]. Its ground state is considered to have a neutron skin structure consisting of four valence neutrons around 4 He with the small binding energy of 3.1 MeV.…”

“…Its ground state is considered to have a neutron skin structure consisting of four valence neutrons around 4 He with the small binding energy of 3.1 MeV. For the excited states of 8 He, most of them can be located above the 4 He + 4n threshold energy [10]. This fact indicates that the observed resonances of 8 He can decay into the channels of 7 He + n, 6 He + 2n, 5 He + 3n, and 4 He + 4n.…”

8He Spectroscopy in Stopped Pion Absorption By 9Be

“…However, evidence of this assumption requires better statistics of measurements. In several works [1,4,8,9] higher excitations were observed. The observed spectrum is limited to the E = 7.5…”

“…Valence nucleons in 8 He are bound stronger than in 6 He (S 2 ( 8 He) = 2.14 MeV, S 2 ( 6 He) = 0. was shown experimentally [3,4] and theoretically [5,6], that along with the (p 3/2 ) 4 component the wave function of the ground state, can contain a noticeable admixture…”