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 CN у104 as well as in the symmetric fusion at Z CN у90. 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 ⌬A. These nuclei gradually lose ͑or acquire͒ their individualities with increasing ͑or decreasing͒ the number of collectivized nucleons ⌬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.

Theoretical study of the synthesis of superheavy nuclei withZ=119and 120 in heavy-ion reactions with trans-uranium targets

“…In this work we assume a tip-tip orientation of the two deformed nuclei and that the dynamical deformations of the two nuclei satisfy [26] with the stiffness parameter C i (i = 1 and 2) calculated from a liquid drop model [40]. We then define δβ ≡ (δβ 1 + δβ 2 )/2 and following Refs.…”

“…the incident energy in the center of mass frame. In this work the capture cross section σ cap is calculated with an empirical coupled channel approach [26,27] and the survival probability W sur is calculated using a statistic model [28,29]. In the fusion process, an excited compound nucleus (CN) may be formed.…”

Role of neutron rearrangement channels in sub-barrier fusion

“…The sub-barrier fusion enhancement induced by coupling of relative motion to surface deformations or rotation of heavy deformed nuclei is well understood and properly described within the quantum coupled channel approach (see e.g. [1][2][3]) and within the empirical coupled channel (ECC) model [4]. At the same time there are many experimental evidences of additional enhancement of the sub-barrier fusion cross section due to neutron rearrangement with positive Q values.…”

Effects of nuclear structure on quasi-fission

“…This is indeed crucial to have reliable theoretical models in order to drive future experiments on heavy elements formation. Macroscopic approaches have been thoroughly used in the past [28,29]. In addition, the recent increase of computational power allowed microscopic descriptions of nuclear dynamics.…”