6,7Li+27Al reactions close to and below the Coulomb barrier

The reactions Li-6,Li-7+Al-27 were compared with the reactions O-17,O-18+O-16 which form the same compound nuclei S-33,S-34. Cross-section data for the reactions Li-6,Li-7+Al-27 were derived from experimentally determined gamma-ray production cross sections for transitions in several residual nuclei. For the reactions O-17,O-18+O-16 experimental results from the literature were used. It could be shown that the weakly bound projectiles Li-6,Li-7 undergo not only fusion processes, but also breakup reactions quite in contrast to the tightly bound projectiles O-18 and O-17, respectively. Especially below the Coulomb barrier such direct reactions play an important role in competition to complete fusion. Calculations based on the statistical model agree well with the available data for O-17,O-18+O-16, but failed to represent the behavior of the experimentally determined production cross sections for the evaporation residues in the reactions Li-6,Li-7+Al-27. But coupled-channel codes and calculations based on a nucleus-nucleus proximity potential are able to reproduce the energy dependence of the complete fusion cross sections.