Fusion-Fission Dynamics of the Synthesis of Super-Heavy Nuclei

Fusion-fission dynamics in the reactions leading to formation of very heavy atomic nuclei is studied. A systematic analysis of the heavy ion fusion reactions is performed within a "standard" theoretical approach without any adjustable parameters and additional simplification. Good agreement with experimental data was obtained in all the cases up to synthesis of the 106 element. A process of the compound nucleus formation, starting from the instant when two heavy nuclei touch and proceeding in strong competition with the fission and quasi-fission processes, plays an important role in the asymmetric synthesis of super-heavy elements with Z_CN > 106 as well as in the symmetric fusion at Z_CN ≥ 90. A new mechanism of the fusion-fission process for a heavy nuclear system is proposed, which takes place in the (A₁, A₂) space, where A₁ and A₂ are two nuclei, surrounded by a certain number of common nucleons ΔA. These nuclei gradually lose (or acquire) their individualities with increasing (or decreasing) the number of collectivized nucleons ΔA. The driving potential in the (A₁, A₂) space is derived, which allows the calculation of both the probability of the compound nucleus formation and the mass distribution of fission fragments in heavy ion fusion reactions.