Influence of the Li-6,Li-7 breakup process on the near barrier elastic scattering by heavy nuclei

Angular distributions of the elastic scattering of the Li-6,Li-7 On Ba-138 were measured, in the energy range 21 less than or equal to E(lab)less than or equal to 32 MeV. The analysis of the data was performed via the optical model, using the Woods-Saxon potential, in order to find the energy depend ence of the real and imaginary parts of the nuclear potential. The existenc e of a threshold anomaly for the Li-7 scattering and its absence for the Li -6 one was observed. It is interpreted that the breakup of Li-6, with disso ciation energy smaller that its first excited state, is responsible for the vanishing of the threshold anomaly. [S0556-2813(99)01404-1].