Investigation of fusion probabilities in the reactions with Cr-52,Cr-54, Ni-64, and Zn-68 ions leading to the formation of Z=120 superheavy composite systems

Background: The formation of superheavy nuclei in fusion reactions is suppressed by a competing quasifission process. The competition between the formation of the compound nucleus and the quasifission depends strongly on the reaction entrance channel. Purpose: The investigation of fission and quasifission processes in the formation of Z = 120 superheavy composite systems in the Cr-52,Cr-54 + Cm-248 and Zn-68+ Th-232 reactions, and their comparison with the Ni-64+ U-238 reaction at energies in the vicinity of the Coulomb barrier. Methods: Mass-energy distributions of fissionlike fragments formed in the reactions Cr-52,Cr-54 + Cm-248 and Zn-68+ Th-232 at energies near the Coulomb barrier were measured using the double-arm time-of-flight spectrometer CORSET. Results: Capture cross sections for the reactions under investigation were measured. The most probable fragment masses and total kinetic energies as well as their variances in dependence on the interaction energy were studied for asymmetric and symmetric fragments. The fusion probabilities were estimated from the analysis of massenergy distributions. Conclusions: The estimated fusion probability drops down by a factor of 10(3) in the Cr-54 + Cm-248 reaction compared to the reactions of Ca-48 ions with actinides. Among the studied reactions, the Cr-54 + Cm-248 is the most favorable one for the production of the superheavy element with Z = 120.