Excitation modes of ${}^{11}$Li at E${}_x\sim$ 1.3 MeV from proton collisions

Abstract

The cross section for p-${}^{11}$Li inelastic scattering at 68 MeV/u 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 ${}^{11}$Li are used to calculate the ${}^{11}$Li(p,p${}^{\prime }$) continuum excitations, and all show peaks below 3 MeV of excitation energy, both in resonant and some non-resonant channels. In the most realistic model of ${}^{11}$Li, there is a strong dipole contribution associated with attractive but not a fully-fledged resonant phase shifts, and some evidence for a J${}_{nn}^{\pi }=0_2^{+}$ 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.

Comments: 4 pages, 3 figures, to be published Phys Rev C, Rapid Communication