The influence of breakup channels on the complete fusion of weakly bound systems is investigated in terms of dynamic polarization potentials. The systematic enhancement of the cross section at sub-barrier energies seems to be consistent with recent experimental observations that nucleon transfer, often leading to breakup, is dominant compared to direct breakup at this energy regime. At energies above the barrier, the repulsive polarization potential due to direct breakup predominates and complete fusion is suppressed.

No abstract

Quasielastic excitation functions for the 16,18 O + 60 Ni systems were measured at energies near and below the Coulomb barrier, at the backward angle θ LAB = 161 • . The corresponding quasielastic barrier distributions were derived. The data were compared with predictions from coupled channel calculations using a double-folding potential as a bare potential. For the 16 O-induced scattering, good agreement was obtained for the barrier distribution by using the projectile default nuclear matter diffuseness obtained from the São Paulo potential systematic, that is, 0.56 fm. However, for the 18 O-induced scattering, good agreement was obtained only when the projectile nuclear matter diffuseness was changed to 0.62 fm. Therefore, in this paper we show how near-barrier quasielastic scattering can be used as a sensitive tool to derive nuclear matter diffuseness.

No abstract

We have performed CDCC calculations for the 6 Li + 59 Co, 144 Sm and 208 Pb systems, to investigate the dependence of the relative importance of nuclear and Coulomb breakup on the target charge (mass) at near barrier energies. The calculations were in good agreement with the experimental elastic scattering angular distributions for these systems and then, their predictions to the nuclear, Coulomb and total breakup were investigated. Although the relative importance of the nuclear breakup is, as expected, larger for lighter targets, this effect is not very pronounced. We also investigate a scaling of the nuclear breakup with the target mass and we compare the predictions for the integrated total breakup cross sections with experimental fusion cross sections at similar energies.

High-precision data of backward-angle elastic and quasielastic scattering for the weakly bound 6 Li projectile on 144 Sm target at deep-sub-barrier, near-, and above-barrier energies were measured. From the deep-sub-barrier data, the surface diffuseness of the nuclear interacting potential was studied. Barrier distributions were extracted from the first derivatives of the elastic and quasielastic excitation functions. It is shown that sequential breakup through the first resonant state of the 6 Li is an important channel to be included in coupled-channels calculations, even at deep-sub-barrier energies.

No abstract

We have analyzed the backward angle quasi-elastic excitation function and the barrier distribution for the 7 Li + 144 Sm system by considering not only the direct breakup of the projectile, the inelastic excitations of the target and the one-neutron transfer channel, but also the sequential breakup of 7 Li as a two-step process: the stripping of one neutron followed by the breakup of 6 Li. The agreement of the theoretical calculations with the experimental barrier distribution is good, even without any fit procedure. This result confirms some recent experimental evidences showing the importance of this two-step process to 7 Li breakup.