Improvement on Fermionic properties and new isotope production in molecular dynamics simulations

TL;DR

This paper enhances quantum molecular dynamics simulations by improving stability and energy conservation, leading to better predictions of fusion cross sections and isotope distributions, and suggesting new pathways for neutron-rich isotope production.

Contribution

The study introduces a momentum transfer consideration in the Fermi constraint, significantly improving the stability and accuracy of quantum molecular dynamics simulations.

Findings

Improved stability of initial nuclei and fragments in simulations.

Better reproduction of fusion cross sections at sub-barrier energies.

Prediction of new neutron-rich isotopes from U+U collisions.

Abstract

By considering momentum transfer in the Fermi constraint procedure, the stability of the initial nuclei and fragments produced in heavy-ion collisions can be further improved in the quantum molecular dynamics simulations. The case of the phase space occupation probability larger than one is effectively reduced with the proposed procedure. Simultaneously, the energy conservation can be better described for both individual nuclei and heavy-ion reactions. With the revised version of the improved quantum molecular dynamics (ImQMD) model, the fusion excitation functions of $^{16}$O+$^{186}$W and the central collisions of Au+Au at 35 AMeV are re-examined. The fusion cross sections at sub-barrier energies and the charge distribution of fragments are relatively better reproduced due to the reduction of spurious nucleon emission. The charge and isotope distribution of fragments in Xe+Sn, U+U and Zr+Sn at intermediate energies are also predicted. More unmeasured extremely neutron-rich fragments with $Z=16-28$ are observed in the central collisions of $^{238}$U+$^{238}$U than that of $^{96}$Zr+$^{124}$Sn, which indicates that multi-fragmentation of U+U may offer a fruitful pathway to new neutron-rich isotopes.