[en] Fission fragment angular correlations for the system ⁵⁸Ni + ²³²Th at 20, 25 and 30 MeV/u show still a bump for large momentum transfers which suggest that its disappearance for the ⁴⁰Ar + ²³²Th system at 44 MeV/u is not due to a limitation in the excitation energy and that the size and velocity of projectiles are also important. High relative velocities of fission fragments are measured for large transfers (approximately 9.5 GeV/c), this could be due to more exotic fission of hot nuclei

[en] Fragment-fragment correlations have been studied in α-induced reactions to incident enrgies from 70 to 800 MeV/u on Ag, Ho and Au targets. Even at the highest energy binary thermal fission is observed with excitation energies up to 800-900 MeV. In addition, events with mass number around 30 and relative velocities up to twice the values expected for thermal fission occur and are attributed to multifragmentation. The energy deposit rather than the projectile velocity seems to be the parameter governing the appearance of the multifragmentation process which competes strongly with fission for imparted energies beyond 800 MeV. (orig.)

[en] Formation and decay properties of composite-like nuclei produced by ⁵⁸Ni projectiles bombarding ²³²Th target nuclei are investigated at different energies by means of fission fragment angular correlation measurements. Experimental results are compared to the exciton model and excitation energies in the fissioning nuclei are deduced. By comparing the present data with the results on other systems, the influences of entrance channel conditions and composite-like nuclei temperatures are discussed to explain the evolution of the high linear momentum transfer region. The coexistence of both massive transfer mechanism and head-on collisions followed by preequilibrium is suggested. (orig.)

[en] Angular correlations between fission fragments induced by an ⁴⁰Ar bombardment of ²³²Th targets at four energies, 31, 35, 39 and 44 MeV/u, have been measured as well as the energies, velocities and masses of both fragments. The characteristics of peripheral collisions remain about constant in the range studied, whereas the component attributed to the central collisions which shows a saturation in linear momentum transfer at 180 MeV/c per incident nucleon, has a cross section decreasing with bombarding energy which is correlated to an increase of the excitation energy of the fissioning nuclei. (orig.)