Role of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>N</mml:mi> <mml:mo>/</mml:mo> <mml:mi>Z</mml:mi> </mml:mrow> </mml:math> equilibration in multinucleon-transfer and fusion processes in collisions of medium-mass sph

Background: Charge equilibration is a crucial phenomenon of nuclear dynamics observed in collisions of heavy nuclei characterized by varying neutron-to-proton ($N/Z$) ratios. This process involves equalizing the $N/Z$ ratios of fragments, which occurs at the initial stage of nuclear reaction.Purpose: This work focuses on a theoretical investigation of the charge equilibration process that occurs during low-energy collisions of heavy nuclei, and on examining its impact on multinucleon transfer and fusion processes.Method: A multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations [A. V. Karpov et al., Phys. Rev. C 96, 024618 (2017)] was employed in this work.Results: A broad set of experimental data on multinucleon transfer products of the $^{40}\mathrm{Ca}, ^{56}\mathrm{Fe}, ^{58}\mathrm{Ni}, ^{64}\mathrm{Ni}+^{208}\mathrm{Pb}$ reactions was analyzed within the dynamical model. The agreement of the calculated energy, atomic number, angular, and isotopic distributions of the reaction products with corresponding experimental data enabled us to refine the model parameters governing the time of nuclear neck evolution and the nucleon transfer rate. Based on this analysis, the mechanism and duration of 0.5 zs for the charge equilibration process were determined. An influence of $N/Z$ equilibration was observed on capture and fusion processes in the $^{40}\mathrm{Ca}, ^{48}\mathrm{Ca}+^{208}\mathrm{Pb}$ reactions.Conclusions: Equilibration of $N/Z$ ratios of fragments is primarily driven by the minimization of the potential energy of the system. This process predominantly occurs along an optimal path, and involves the redistribution of neutrons and protons between the fragments in opposite directions. The products formed in these multinucleon transfer channels exhibit increased cross sections. The decrease in the potential energy of the system during the charge equilibration leads to an enhancement of multinucleon transfer and fusion processes, which are particularly evident at energies below the potential barrier.