Dissipative collisions between complex nuclei. The frontier between complete and incomplete fusion

It is known since the early work of Miller et al., that high angular momenta inhibit complete fusion. This has been expressed as a l-cut-off for complete fusion (lsub(crit)), above which the centrifugal potential is so large that it prevents attractive fusion between the two colliding nuclei. The sharp cut-off model calculates the cross section for complete fusion as a summation of partial-waves up to a limit (lsub(crit)) the origin of which has been widely discussed. We have developped, in 1974, the concept of critical distance which seems to be quite a valuable parameter at least for c.m. energies below 6 to 8 MeV per nucleon. We would like to discuss here to which extent is correct the concept of very sharp cut off, and to show that for l near lsub(cr) several phenomena might appear, particularly when the colliding energy increases, which may attenuate a very strong statement on the exact location at which one passes from a l value leading to complete fusion to a l value leading to deep inelastic transfer. (orig.)