Deep insight into charge equilibration and the effects on producing neutron-rich isotopes around N = 126 in the multinucleon transfer reactions

TL;DR

This study investigates charge equilibration mechanisms in multinucleon transfer reactions using advanced models, revealing incomplete and inverse charge equilibration behaviors that influence the production of neutron-rich isotopes near N=126.

Contribution

It introduces a detailed analysis of charge equilibration dynamics with the DNS-sysu and ImQMD models, providing new insights into the process and its impact on isotope production.

Findings

Incomplete charge equilibration observed even in deep collisions.

Identification of fast equilibration with a characteristic time of ~0.52 zs.

Clarification of the correlation between charge equilibration and mass asymmetry.

Abstract

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 Letter, 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 the 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 $^{140}$Xe + $^{198}$Pt. Unlike the slow process presented in the ImQMD model, the behavior of fast equilibration with the characteristic time $\sim$ 0.52 zs is obtained based on the DNS-sysu model, which is consistent with the experimental data. By performing the 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 provides essential information for producing the neutron-rich isotopes around $N = 126$.