HALO EXCITATION OF HE-6 IN INELASTIC AND CHARGE-EXCHANGE REACTIONS

Four-body distorted wave theory appropriate for nucleon-nucleus reacti ons leading to three-body continuum excitations of two-neutron Borrome an halo nuclei is developed. The peculiarities of the halo bound state and three-body continuum are fully taken into account by using the me thod of hyperspherical harmonics. The procedure is applied for A=6 tes t-bench nuclei; thus we report detailed studies of inclusive cross sec tions for inelastic He-6(p,p')He-6 and charge-exchange Li-6(n,p)He-6* reactions at nucleon energy 50 MeV. The theoretical low-energy spectr a exhibit two resonancelike structures. The first (narrow) is the exci tation of the well-known 2(+) three-body resonance. The second (broad) bump is a composition of overlapping soft modes of multipolarities 1( -),2(+),1(+),0(+) whose relative weights depend on transferred momentu m and reaction type. Inelastic scattering is the most selective tool f or studying the soft dipole excitation mode.