Synthesis of superheavy nuclei: Nucleon collectivization as a mechanism for compound nucleus formation

Abstract

A consistent systematic analysis of the synthesis of very heavy nuclei 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 102 element. It was confirmed that 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 quasifission processes, plays an important role in the asymmetric synthesis of superheavy elements with ${Z}_{\mathrm{CN}}>~104$ as well as in the symmetric fusion at ${Z}_{\mathrm{CN}}>~90.$ A new mechanism of the fusion-fission process for a heavy nuclear system is proposed, which takes place in the ${(A}_{1}, {A}_{2})$ space, where ${A}_{1}$ and ${A}_{2}$ are two nuclei, surrounded by a certain number of common nucleons $\ensuremath{\Delta}A.$ These nuclei gradually lose (or acquire) their individualities with increasing (or decreasing) the number of collectivized nucleons $\ensuremath{\Delta}A.$ The driving potential in the ${(A}_{1}, {A}_{2})$ 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.