Quasi-free scattering with 6,8He beams

This paper presents the results of experimental investigations of (p,pn), (p,pα) and (p,p 6He) reactions with relativistic 6He and 8He beams impinging on a hydrogen target. Information on the structure of extremely neutron-rich nuclei was obtained by using the unique characteristic of quasi-free scattering processes and inverse kinematics. For the first time, momentum distributions of complex clusters inside 6He and 8He were measured. Spectroscopic factors for valence neutrons, α- and 6He clusters were deduced from the experimental data. They demonstrate that the filling of the p12 shell is the essential feature of the 8He structure. It is shown that the 8He cluster structure can be considered as a 6He core plus two valence neutrons.