Excitation modes of 11Li at Ex∼1.3 MeV from proton collisions

The cross section for p-11Li inelastic scattering at 68 MeV/nucleon is evaluated using the multiple scattering expansion of the total transition amplitude (MST) formalism, and compared with the breakup in the shakeoff approximation. Three different potential models for 11Li are used to calculate the 11Li(p,p') continuum excitations, and all show peaks below 3 MeV of excitation energy, both in resonant and some nonresonant channels. In the most realistic model of 11Li, there is a strong dipole contribution associated with attractive but not a fully-fledged resonant phase shifts, and some evidence for a Jnnπ=02+ resonant contribution. These together form a pronounced peak at around 1-2 MeV excitation, in agreement with experiment, and this supports the use of the MST as an adequate formalism to study excited modes of two-neutron nuclear halos