Energy dependence of nucleus-nucleus potential close to the Coulomb barrier

TL;DR

This study investigates how nucleus-nucleus interaction potentials vary with energy near the Coulomb barrier using microscopic time-dependent Hartree-Fock theory, revealing energy-dependent dynamical effects that influence fusion processes.

Contribution

It provides a detailed microscopic analysis of energy dependence in nucleus-nucleus potentials near the Coulomb barrier, highlighting dynamical effects absent in static models.

Findings

Potentials match frozen density approximation at high energies.

Potentials become energy dependent near the Coulomb barrier.

Dynamical reorganization reduces the effective fusion barrier by 2-3%."

Abstract

The nucleus-nucleus interaction potentials in heavy-ion fusion reactions are extracted from the microscopic time-dependent Hartree-Fock theory for mass symmetric reactions $^{16}$O${}+^{16}$O, $^{40}$Ca${}+^{40}$Ca, $^{48}$Ca${}+^{48}$Ca and mass asymmetric reactions $^{16}$O$ +^{40,48}$Ca, $^{40}$Ca${}+^{48}$Ca, $^{16}$O+$^{208}$Pb, $^{40}$Ca+$^{90}$Zr. When the center-of-mass energy is much higher than the Coulomb barrier energy, potentials deduced with the microscopic theory identify with the frozen density approximation. As the center-of-mass energy decreases and approaches the Coulomb barrier, potentials become energy dependent. This dependence signs dynamical reorganization of internal degrees of freedom and leads to a reduction of the "apparent" barrier felt by the two nuclei during fusion of the order of $2-3 %$ compared to the frozen density case. Several examples illustrate that the potential landscape changes rapidly when the center-of-mass energy is in the vicinity of the Coulomb barrier energy. The energy dependence is expected to have a significant role on fusion around the Coulomb barrier.