  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.
