Dynamics of charge equilibration and effects on producing neutron-rich isotopes around N=126 in multinucleon transfer reactions

The dynamics of the charge equilibration (CE) and the effects on the production of the neutron-rich isotopes around N = 126 in multinucleon transfer reactions are still not well understood. In this work, we investigate the mechanism of the CE from different viewpoints by using the extended version of the dinuclear system model (DNS-sysu) and the improved quantum molecular dynamics (ImQMD) model. From the macroscopic and microscopic dynamical viewpoints, we find incomplete CE for the mass asymmetry reaction systems even in very deep collisions, and the behavior of "inverse CE" that the tendency of the fragments is away from the N/Z value of the compound system in the reaction 140Xe + 198Pt. Unlike the slow process presented in the ImQMD model, the behavior of fast equilibration with the characteristic time approximate to 0.52 zs is obtained based on the DNS-sysu model, which is consistent with the experimental data. By performing a systematic calculation, the correlation between the CE and the mass asymmetry of the reaction systems is clarified, which not only accounts for the observed intriguing phenomena of the CE but also sheds light on the optimal combinations for producing the neutron-rich isotopes around N = 126.