FUSION AROUND THE BARRIER IN BE-11,BE-9-209(BI)

The Be-9 + Bi-209 fusion cross sections were measured in the range 37. 5 MeV less than or equal to E-lab less than or equal to 45.0 MeV at th e Munich Tandem via the observation of ground state alpha-decay of the evaporation residues. Fusion cross sections of Bi-209 with the ''halo '' Be-11 unstable projectile in the region around the Coulomb barrier were deduced from an experiment done with the same technique at the RI KEN Ring Cyclotron. Above the Coulomb barrier the Be-11 cross sections are larger than the Be-9 ones in agreement with theoretical predictio ns based on the larger Be-11 halo radius. Also below the barrier these theories foresee the same behavior in disagreement with the experimen tal results, since the two cross sections are rather similar.