Fusion and reactions of exotic nuclei

Close to the drip lines, the scattering cross sections of halo nuclei show a different behaviour as compared to the tightly bound projectiles of the stability line. Several experiments carried out in the last decade have been dedicated to investigate the competition between transfer, breakup and fusion channels at energies around and below the Coulomb barrier. The rather complex scenario gives rise to conflicting conclusions concerning the effect of breakup and transfer on reaction dynamics and the sub-barrier fusion process. In this work we discuss recent experimental findings in fusion and reactions of 6He halo nucleus at energies around the Coulomb barrier. Data on elastic cross sections show a strong absorption pattern originated by coulomb dipole couplings and the effect of the coupling to the states of the continuum. Large alpha yields are obtained from neutron transfer mechanisms appearing mainly at backward angles. The fusion cross sections show a clear enhancement at deep sub-barrier energies with respect the tightly bound system 4He+208Pb. The angular distributions of elastic and alpha yields, relative to Rutherford, show interesting regularities when they are represented in terms of the distances of closest approach. In the fusion process static and dynamical effects clearly appear when proper scaling is introduced. The reaction cross sections can be described by a parameterization based on Wong's formula by using suitable scaling parameters, and halo-core decoupling seems to be a useful concept for describing the reactions of halo systems