7Be versus 7Li:: The influence of breakup threshold on the dynamic polarization potential -: art. no. 044605

Previous continuum-discretized coupled-channel (CDCC) calculations comparing Li-6+Pb-208 with Li-7+Pb-208 suggested that the observed difference in the dynamic polarization potentials for these systems at bombarding energies close to the Coulomb barrier was due to the similar to1 MeV difference between the alpha+d and alpha+t breakup thresholds for Li-6 and Li-7 rather than differences in their ground state structures. In this work we compare CDCC calculations for Be-7+Pb-208 with similar calculations for Li-7+Pb-208 to further test whether the breakup threshold is the controlling factor in determining the near-barrier behavior of the dynamic polarization potential. We conclude that this is indeed the case and that Be-7, with its lower breakup threshold, will behave like Li-6 rather than Li-7, in that it will not exhibit a threshold anomaly. Furthermore, we predict a clear experimental signature for this difference in behavior: the lack of a pronounced Coulomb rainbow in the Be-7 elastic scattering angular distributions. It is proposed that elastic scattering measurements of Be-7+Pb-208 be carried out at two energies near the Coulomb barrier to confirm this conclusion.