Shell effects in fission and quasi-fission of heavy and superheavy nuclei

Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions C-12+Pb-204, Ca-48+Sm-144,Sm-154, Er-168, Pb-208 U-238, Pu-244, Cm-248; Fe-58+Pb-208, Pu-244, Cm-248, and Ni-64 +W-186, Pu-242 are presented in the work. The choice of the above-mentioned reactions was inspired by recent experiments on the production of the isotopes (283)112, (289)114 and (283)116 at Dubna [1],[2] using the same reactions. The Fe-58 and Ni-64 projectiles were chosen since the corresponding projectile-target combinations lead to the synthesis of even heavier elements. The experiments were carried out at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR, Russia), the XTU Tandem accelerator of the National Laboratory of Legnaro (LNL, Italy) and the Accelerator of the Laboratory of University of Jyvaskyla (JYFL, Finland) using the time-of-flight spectrometer of fission fragments CORSET[3] and the neutron multi-detector DEMON[4],[5]. The role of shell effects and the influence of the entrance channel on the mechanism of the compound nucleus fusion-fission and the competitive process of quasi-fission are discussed.