Direct Experimental Evidence for a Soft-Dipole Response in ⁶ He

Abstract

The differential cross-sections of the charge exchange reaction 6Li(7Li, 7Be) 6He were measured at beam energies 78 and 82 MeV. In addition to the 0+ bound state and sharp 2+ resonance, three wide bumps were identified in the experimental continuum spectrum of 7Be at small angles. The maximum at excitation energy of ∼ 6 MeV (Γ ∼ 5 MeV FWHM) is consistent with a soft-dipole response, expected in nuclei with neutron halo.