Effects of weakly coupled channels on quasielastic barrier distributions

Heavy-ion collisions often produce fusion barrier distributions with structures displaying a fingerprint of couplings to highly collective excitations. Similar distributions can be obtained from large-angle quasielastic scattering, although in this case, the role of the many weak direct-reaction channels is unclear. For Ne-20+Zr-90, we have observed the barrier structures expected for the highly deformed neon projectile; however, for Ne-20+Zr-92, we find significant extra absorption into a large number of noncollective inelastic channels. This leads to smearing of the barrier distribution and a consequent reduction in the resolving power of the quasielastic method.