Angular Momentum and Cross Sections for Fusion with Weakly Bound Nuclei: Breakup, a Coherent Effect

Results for the cross section and average angular momentum for complete fusion at energies around the Coulomb barrier are presented for ⁷Li with ¹⁶⁵Ho. Comparison of the cross sections with a one-dimensional barrier penetration model, using a potential consistent with the measured elastic scattering, showed a reduction above the barrier and an enhancement below it. An increase in the measured average angular momentum, 〈ℓ〉, above the barrier and its consistency with that obtained from the fusion excitation function for weakly bound nuclei, is reported. These results together with a reanalysis of existing data conclusively demonstrate that the effect of breakup on fusion is coherent, like coupling to any nonelastic channel.