New surface phenomena in heavy-ion-induced reactions

Recent studies of elastic and inelastic scattering at far backward angles for mass-asymmetric heavy-ion systems and of related excitation functions in transfer reactions are considered. The data obtained have uncovered some deficiencies in the present optical description of the ion-ion potential and consequently are likely to provide a more refined understanding of these interactions. New developments examined include (a) the observation of structure in the backward-hemisphere angular distributions for systems such as 12C + 28Si and 16O + 28Si, in particular a sharp rise in cross section at 1800; (b) the presence of broad, resonance-like structure (width 1-2MeV) in the elastic and inelastic excitation functions near 1800; (c) the observation of similar and probably related broad structure in the energy dependence of α-transfer reactions in the forward as well as backward hemispheres. (U.K.)