Investigation of sequential fission of heavy nuclei

Sequential fission was investigated in the reaction 238U + 248Cm at 8.43 MeV/u. From the absence of Coulomb final state interactions a time limit of 1-1.5 x 10-20 s is deduced for the lifetime of intermediate fissioning systems with Z up to 120. The angular distributions of sequential fission in the reaction of 208Pb + 90Zr were studied vs. energy loss. In-plane anisotropies of proportional 1:2 are found at moderate energy losses which decrease and even change sign towards larger energy losses. In the system U + U at 7.5 MeV, sequential fission events associated with low excitations were investigated. The fission probability, measured down to 10-3 for scattering angles forward of grazing, behaves as expected for compound fission induced by Coulomb excitation. (orig.)