Refractive versus resonant diffraction scattering of loosely bound6Li nuclei

We present a complete analysis of ${\phantom{\rule{0.16em}{0ex}}}^{6}\mathrm{Li}+{}^{16}\mathrm{O}$ elastic scattering at 4 and 5 MeV/nucleon. Using either traditional Woods-Saxon or a range of semimicroscopic folding form factors we find that the data require deep, highly transparent potentials. Physically relevant solutions are selected according to the dispersion relation. The intermediate angle structures and the oscillatory increase of the cross section at large angles are interpreted either as a pre-rainbow oscillation resulting from the interference of the barrier and internal barrier far-side scattering subamplitudes or, equally well, as a resonant diffraction arising from two Regge poles located in peripheral waves. Both semiclassical and Regge pole approaches allow a dynamical separation of the resonant component of the $S$ matrix.