Pauli energy contribution to nucleus-nucleus interaction

TL;DR

This paper investigates how protons and neutrons contribute to Pauli repulsion in nucleus-nucleus interactions, using the Pauli kinetic energy approach within dynamical models, revealing significant differences in their roles during nuclear collisions.

Contribution

It introduces a detailed analysis of proton and neutron contributions to Pauli repulsion using the PKE method in dynamical nuclear models, highlighting their distinct roles in nuclear interactions.

Findings

Neutron contributions to Pauli repulsion are larger in neutron-rich systems.

Dynamical effects reduce Pauli repulsion near the barrier.

Protons and neutrons have different roles in the interaction potential.

Abstract

Background: The Pauli exclusion principle plays a crucial role as a building block of many-body quantal systems comprised of fermions. It also induces a "Pauli repulsion" in the interaction between di-nuclear systems. It has been shown in [Phys. Rev. C 95, 031601 (2017)] that the Pauli repulsion widens the nucleus-nucleus potential barrier, thus hindering sub-barrier fusion. Purpose: To investigate the proton and neutron contributions to the Pauli repulsion, both in the bare potential neglecting shape polarization and transfer between the reactants, as well as in the dynamical potential obtained by accounting for such dynamical rearrangements. Methods: As the basis of our study we utilize the Pauli kinetic energy (PKE) obtained by studying the nuclear localization function (NLF). Recently this approach has been generalized to incorporate all of the dynamical and time-odd terms present in the nuclear energy density functional. This approach is employed in the DCFHF and DC-TDHF methods. Results: The PKE spatial distribution shows that a repulsion occurs in the neck between the nuclei when they first touch. Inside the barrier, neutrons can contribute significantly more to the Pauli repulsion in neutron-rich systems. Dynamical effects tend to lower the Pauli repulsion near the barrier. Proton and neutron dynamical contributions to the PKE significantly differ inside the barrier for asymmetric collisions, which is interpreted as an effect of multinucleon transfer. Conclusions: The PKE is shown to make a significant contribution to nuclear interaction potentials. Protons and neutrons can play very different roles in both the bare potential and in the dynamical rearrangement. Further microscopic studies are required to better understand the role of transfer and to investigate the effect of pairing and deformation.