Elastic scattering for the system 11Be+209Bi at Coulomb barrier energies

The elastic scattering process for 11Be ions impinging on a 209Bi target was studied in the energy range around the Coulomb barrier. The angular distributions of the 11Be scattered particles were analyzed within the optical model framework in order to evaluate the reaction cross section, which turned out to be much larger than the fusion one, especially in the sub-barrier region. The comparison with the system 9Be + 209Bi showed that the reaction cross section is larger for the reaction 11Be + 209Bi in the energy range around the Coulomb barrier, while they are rather similar at higher bombarding energies. This result suggests that direct processes related to the 11Be halo structure and lower binding energy are more relevant at near-barrier energies.