HEAVY-ION SCATTERING AND REACTIONS NEAR THE COULOMB BARRIER AND THRESHOLD ANOMALIES

The couplings between the various reaction channels available for the collision of two heavy ions become especially important at energies near the top of their mutual Coulomb barrier. In particular, they result in a "threshold anomaly" in the dependence of energy of the optical model potential that describes their elastic scattering and a strong enhancement of their fusion cross sections in this energy region. The evidence for these "anomalies" is reviewed and their theoretical explanation is discussed. A dispersion relation between the real and imagery parts of the optical model potential is described and its use is illustrated. Finally, an extension of the one-channel optical model that allows for simultaneous analysis of fusion and elastic scattering is presented and its applications are considered.