Fusion-fission of superheavy compound nuclei produced in reactions with heavy ions beyond Ca

Total Kinetic Energy - Mass distributions of fission-like fragments for the reactions of 22Ne, 26Mg, 36S, 48Ca, 58Fe and 64Ni ions with actinides leading to the formation of superheavy compound systems with Z=108-120 at energies near the Coulomb barrier have been measured. Fusion-fission cross sections were estimated from the analysis of mass and total kinetic energy distributions. It was found that the fusion probability drops by three orders of magnitude for the formation of the compound nucleus with Z=120 obtained in the reaction 64Ni+238U compared to the formation of the compound nucleus with Z=112 obtained in the reaction 48Ca+238U at the excitation energy of the compound nucleus of about 45 MeV. From our analysis it turns out that the reaction 64Ni+238U is not suitable for the synthesis of element Z=120. (authors)