Fusion and reseparation dissipative collision mechanisms between nuclei at energies below 15 MeV.A

Two parameters are relevant in dissipative collisions between complex nuclei. The velocity at the contact, presented in terms of eta'=Z1Z2e2/hV', and the effective fissility (Z2/A)sub(eff). Three different limits are considered for complete fusion. The Yrast line in the compound nucleus, the fission barrier equal to zero in the rotating liquid drop model, and the critical distance. The ''extra-push'' bidimensionnal model of Swiatecki is compared to those limits. It is shown that for light ions at higher energies, the excess of nucleon velocity might be the crucial limit for fusion, instead of the angular momentum. The interest of measuring linear momentum transfers is emphasized. The main features of Deep Inelastic Reactions are described briefly, with a few remarks on the correlation between eta' and the orbiting, on the absence of drift towards mass and Z symmetry. At once, the energy is shared equally between the two fragments and only later on equilibration amongst the nucleons results into an uniform temperature. Finally new progress in the N/Z equilibration are discussed. The concluding part tries to stress prospects for studies on reaction mechanisms in the low energy range