Reaction mechanisms involving weakly bound ⁶Li and ²⁰⁹Bi at energies near the Coulomb barrier

Abstract

The elastic, inelastic, and transfer cross sections are measured for the ⁶Li+²⁰⁹Bi reaction at energies around the Coulomb barrier. The optical model analysis of elastic scattering shows a breakup threshold anomaly in the energy dependence of the real and imaginary potentials. The observed energy dependence is found to be consistent with the dynamic polarization potential obtained from the coupled-channels calculations that explain the above measured reaction channels simultaneously. A comparison of different reaction probabilities reveals that the relative contribution of breakup starts increasing at energies below the Coulomb barrier, in contrast to the behavior of other reaction channels, which get closed as energy is lowered. The large probability of projectile breakup at sub-Coulomb energies leads to the observation of a nonzero imaginary potential even at El_ab0.8V_B.