Fusion and breakup of weakly bound nuclei

Abstract

In this review the phenomenon of heavy-ion fusion at low energies is discussed in detail, with special emphasis given to the fusion of loosely bound stable and unstable projectiles. Experimental results on fusion and breakup of systems such as 6Li, 7Li, 9Be, the two-neutron halo nuclei 6He, the one-neutron halo nucleus 11Be and the one-proton halo nucleus 8B on light, medium and heavy targets are reviewed. An extensive review of the experimental methods and techniques used to measure the fusion and the breakup cross section is also presented, and the experimental challenges encountered in the measurement of the fusion cross section of these systems are pointed out. The theoretical description of the fusion of these loosely bound nuclei with a variety of targets is reviewed. Approaches based on the dynamic polarization potential arising from the strong coupling of the entrance channel to the breakup channel, as well as the Continuum Discretized Coupled Channels method are described at length. In contrast to the fusion of tightly bound projectiles, where enhancement of the complete fusion cross section at sub-barrier energies has been confirmed in the past, the fusion of loosely bound nuclei may exhibit hindrance effects, whose intensity is directly related to the Q -value of the breakup channel. The flux which is removed from the complete fusion channel feeds into what came to be known as the incomplete fusion channel. The elastic scattering of these systems is shown to shed light into the nature of the breakup polarization effect responsible for the fusion hindrance.