Modes of massive nucleon transfer appearing in quasifission processes for collisions of superheavy nuclei

Abstract

Background: It is challenging to distinguish between fusion-fission and quasifission experimentally. To determine the characteristics of quasifission processes associated with dominant phenomena in heavy-ion collisions is important for estimating precisely the fusion cross section, which is relevant to the synthesis of new elements. We classified fusion-fission and quasifission processes theoretically in the past for an accurate assessment of the fusion cross section [Y. Aritomo and M. Ohta, Nucl. Phys. A 744, 3 (2004)]. However, no detailed analysis focused on each process was performed.Purpose: In this work, we aimed to analyze the dynamical characteristics of quasifission processes in terms of the Langevin equation model. We specify the quasifission processes, and analyze the scission configuration. Finally, we clarify the origin of several modes included in quasifission.Method: The calculation framework is the multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations.Results: It is shown that several quasifission modes exist leading to different fragment deformations. The timescale of the quasifission process differs for several different modes. Each scission configuration and total kinetic energy also differ.Conclusions: The different quasifission modes are caused by the neck relaxation controlling the mass drift toward symmetry. This means that it is possible to discuss the time-dependent functional form of the neck parameter $\ensuremath{\epsilon}$ for the quasifission process in the framework of the dynamical model based on Langevin equations.