Role of N/Z equilibration in multinucleon-transfer and fusion processes in collisions of medium-mass spherical nuclei with 208Pb


Saiko V.V. Karpov A.V.
11 December 2025American Physical Society

Physical Review C
2025#112Issue 6

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 40Ca, 6Fe, 8Ni, 64Ni + 208Pb 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 40Ca, 48Ca + 208Pb 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.



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Flerov Laboratory of Nuclear Reactions, JINR, Dubna, 141980, Russian Federation
Institute of Nuclear Physics, Atomic Energy Agency of the Republic of Kazakhstan, Almaty, 050032, Kazakhstan
Dubna State University, Dubna, 141982, Russian Federation

Flerov Laboratory of Nuclear Reactions
Institute of Nuclear Physics
Dubna State University

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