Refractive effects in the scattering of loosely bound nuclei

A study of the interaction of the loosely bound nuclei Li-6,Li-7 at 9 and 19 MeV/nucleon with light targets has been undertaken. With the determination of unambiguous optical potentials in mind, elastic data for four projectile-target combinations and one neutron transfer reaction C-13(Li-7,Li-8)C-12 have been measured over a large angular range. The kinematical regime encompasses a region where the mean field (optical potential) has a marked variation with mass and energy, but turns out to be sufficiently surface transparent to allow strong refractive effects to be manifested in elastic scattering data at intermediate angles. The identified exotic feature, a "plateau" in the angular distributions at intermediate angles, is fully confirmed in four reaction channels and is interpreted as a prerainbow oscillation resulting from the interference of the barrier and internal barrier far-side scattering subamplitudes.