The near-barrier and sub-barrier fusion of light unstable nuclei and their respective stable isotopes with heavy targets ${(}^{4,6}\mathrm{He}{+}^{209}\mathrm{Bi},$ ${}^{4,6}\mathrm{He}{+}^{238}\mathrm{U},$ ${}^{9,11}\mathrm{Be}{+}^{209}\mathrm{Bi},$ and ${}^9\mathrm{Be}{+}^{208}\mathrm{Pb})$ is investigated via coupled channel calculations. The entrance channel optical potential is generated via a microscopic BDM3Y1 interaction. A rather satisfactory description of the experimental data is obtained under the condition that the real part of the optical potential has to be reduced for the weakly bound and halo systems. This reduction proves to be the fundamental difference in treating stable and weakly bound nuclei, and can be attributed to the loss of a flux due to breakup effects.

• Received 23 January 2002

DOI:https://doi.org/10.1103/PhysRevC.65.054606