Complete and incomplete fusion in heavy-ion collisions

This is a survey of the work done at Orsay on the accelerator ALICE, on reactions induced by very heavy ions. (Ar to Kr). It deals mainly with the questions of complete fusion and very inelastic exchanges of nucleons which are relevant to the problem of nuclear viscosity. New results are presented on the very inelastic processes which produce light fragments in Ar-induced reactions on Ni and Th targets. The angular and mass correlation has been verified between the light and the heavy partner, and it is now entirely proven that a large amount of energy is dissipated into intrinsic excitations. Measured cross sections for complete fusion are compiled and a number of comments are given on the limitation for fusion in relation to critical angular momenta and critical distances of approach. For reactions induced by krypton and copper ions, the fusion barrier is higher than the interaction barrier. Below the fusion barrier, peculiar phenomena occur, named "quasi-fission". The fusion barrier is explained in terms of a cut-off in the lowlℏpopulation for partial waves of the incoming ion, due to friction forces.