Linear momentum transfer studies at energies around 100 MeV/u

In nucleus-nucleus collisions above the Fermi velocity a transition from nucleus-nucleus collisions to nucleon-nucleon interactions is expected. The study of this transition is the subject of the experimental program at Saturne II which up to now has been carried out using light projectiles and at GANIL with heavy projectiles. In order to characterize the reaction mechanisms, the linear momentum transferred from the projectile to the target is used. This quantity is accessible by the measurement of the angle and velocities of the fission fragments. By the use of heavy targets such as Th nearly all reactions terminate by fission and a general view of the occuring mechanisms can be obtained. Detailed information is obtained if lighter target nuclei are used whereby fission is less probable and only a selected range of impact parameters leads to fission or by precisely measuring all kinematic quantities in order to reconstruct the event. These various aspects mark the structure of this talk. In the first part, based on the measurements on Th, a classification of the reaction mechanisms is proposed, and in the second part data on lighter nuclei are discussed whereby high transferred momenta are selected and the precise measurements performed at GANIL are presented