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Abstract.We have performed precision elastic backscattering measurements for the weakly bound nuclei 6,7 Li on the medium and heavy mass targets 58 Ni, 116,120 Sn and 208 Pb at sub-and near-barrier energies (E c.m./Vbar = 0.6 to 1.3). Excitation functions of elastic scattering cross-sections have been measured at ±160• and ±170• and the corresponding ratios to Rutherford scattering and relevant barrier distributions have been extracted. These measurements complement recent work on a 28 Si target, for probing systematically the potential at sub-and near-barrier energies and relevant reaction mechanisms, while indicate a possible breakdown of the dispersion relation.

The excitation functions for 7 Li + 28 Si quasielastic scattering at 150 • and 170 • have been measured at suband near-barrier energies (0.6 to 1.3 V B ) and the corresponding barrier distributions derived. The results were analyzed within the framework of the optical model using a procedure similar to one used on previous results for 6 Li + 28 Si employing double-folded potentials calculated using the BDM3Y1 effective interaction. The variation of the surface strength of the optical potential as a function of incident energy was compared for the two systems 6 Li + 28 Si and 7 Li + 28 Si, the barrier distributions being used to help better define the potential at the lowest energies. The barrier distributions were also analyzed with continuum-discretized coupled-channel (CDCC) and coupled reaction channel (CRC) calculations as a means of investigating the influence of breakup and transfer reactions on these quantities for these light, weakly bound projectiles.

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