Microscopic-macroscopic features in fusion reactions involving light systems

Experimental results obtained at Argonne and elsewhere for the fusion cross-section energy dependence for light to medium weight systems are presented. The most notable features in these data are the observation of (1) oscillatory structure in the fusion cross section excitation function for those systems involving the most tightly bound nuclei in the 1p shell and (2) sudden increases in the maximum fusion cross section for systems which involved nuclei differing only by one or two nucleons. Comparisons of the experimental cross-section behaviors in both the low-energy and high-energy regions with macroscopic model predictions show that significant discrepancies exist. The possible importance of the structure of the projectile and target on this cross-section behavior is discussed. From these data it appears that there is ample evidence that the detailed structure of the projectile and target play an important role in the fusion process. These results indicate that more high-quality data sensitive to these ''microscopic'' features, and theoretical calculations which attempt to include the detailed structure of the interacting ions are needed for progress in understanding these phenomena