New modes of halo excitation in the He-6 nucleus

Predictions are made for the structure of a second 2(+) resonance, the soft dipole mode and unnatural parity modes in the He-6 continuum. We use a structure model which describes the system as a three-body alpha+N+N cluster structure, giving the experimentally known properties of He-6 and Li-6, and use the distorted-wave impulse approximation (DWIA) reaction theory appropriate for dilute matter. The presence of both resonant and nonresonant structures in the halo excitation continuum is shown to be manifest in charge-exchange reactions as well as inelastic scattering with single nucleons.