Measuring barriers to fusion

The experimental extraction of detailed barrier distributions has brought a significant advance in the study of the fusion of heavy nuclei, and indeed in the entire heavy-ion reaction process. A quantitative understanding of the entrance-channel effects induced by target and projectile structure has emerged, based on recent high-precision measurements of fusion excitation functions. These distributions show clearly whether the experimental data are good enough to give the information required. They are also the functions best suited to the theoretical interpretation of the reaction dynamics-often presenting an unambiguous "fingerprint" of the target and projectile structure. We are now at the stage where we can start to exploit the insights gained in order to understand properties of the compound nucleus created: its spin distribution and evaporation residues, perhaps its possible shapes, and, in the case of heavy systems, its subsequent fission.