IMPORTANCE OF NONLINEAR COUPLINGS IN FUSION-BARRIER DISTRIBUTIONS ANDMEAN ANGULAR MOMENTA

The effects of higher-order coupling of surface vibrations to the rela tive motion on heavy-ion fusion reactions at near-barrier energies are investigated. The coupled-channels equations are solved to all orders , and also in the linear and the quadratic-coupling approximations. It is shown that the shape of fusion-barrier distributions and the energ y dependence of the average angular momentum of the compound nucleus c an significantly change when the higher-order couplings are included. The role of octupole vibrational excitation of O-16 in the O-16 + Sm-1 44 fusion reaction is also discussed using the all-order coupled-chann els equations.