THE ORIGIN OF SYMMETRICAL SPLITTING EVENTS IN THE S-32+NI-58, NI-64 REACTIONS AT 160 AND 180 MEV

Gamma-multiplicity M-gamma and missing charge DELTA-Z from fragment-fragment coincidences have been measured for fissionlike events in the reactions S-32 + Ni-58,64 at 160 and 180 MeV bombarding energies. The experimental data have been compared with a Monte Carlo simulation of the sequential decay of primary fragments assumed to be in thermal equilibrium. Statistical-model calculations have been performed with different assumptions on the spin distribution of the composite system decaying in two symmetric fragments. The experimental M-gamma data are well described by model calculations with spin values inside the region. Those spin values are close to the first moments of the angular-momentum distributions for fusion-fission of the compound nucleus as computed by statistical model using finite-range corrected fission barriers. Model calculations describe also well the experimental DELTA-Z values for the S-32 + Ni-58 reaction but overestimate the data relative to the 64Ni target, evidencing difficulties in the complete reconstruction of the sequential decay of the reaction products.