Article révisé par les pairs
Résumé : Cross sections have been measured for argon-induced fission following full momentum transfer. Two incident energies (between 200 and 300 MeV) have been used for 238U, 209Bi, 165Ho and natMo targets. For a natSb target, the fission excitation function has been measured from 160 to 300 MeV. The experimental method was an improved version of the angular correlation method, which takes into account kinetic energies and time-of-flight correlations. This allowed us to eliminate fission events following transfer reactions and also random events. Assuming that the angular distribution is that characteristic of fission fragments issued from a compound nucleus (close to 1/sinθ) the fission cross sections range from 10 ± 1 mb for Ar + Mo at 200 MeV to 1030 ± 120 mb for Ar + U at 300 MeV. When necessary, these cross sections have been added to the cross sections for the formation of evaporation-residue nuclei measured by other authors in order to obtain complete-fusion cross sections. The deduced critical angular momentum for formation of a complete-fusion nucleus are found to be an increasing function of the mass and energy of the incoming particle. These results are used to test the concept of a critical distance of approach which would govern fusion between two complex nuclei. The threshold of the excitation function measured for Ar + Sb is compared with calculations based on the statistical model for the competition between fission and evaporation. These calculations include the effects of multiple-chance fission and of angular momentum on fission widths. © 1975.