Probing the surface properties of proton-rich nuclei with the yield ratios of neutrons and protons in intermediate-energy heavy-ion collisions

Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model, we investigate the yield ratios of neutron-proton $[R(n/p)]$ in the peripheral collisions of neutron-deficient $^{48,50,52,54,56,58}\mathrm{Ni}+^{58}\mathrm{Ni}$ systems at beam energy of 400 MeV/nucleon. The short-range correlation (SRC) induced by the tensor force in the isosinglet neutron-proton interaction channel is incorporated into the extended Thomas-Fermi approximation (ETF*) for the nucleon kinetic-energy density in finite nuclei. This leads to a neutron skin in momentum ($k$) space for neutron-deficient nucleus. It is shown that the $R(n/p)$ from different neutron-deficient Ni projectiles follows a negative exponential trend with their proton skin thickness. However, when considering the neutron skin in $k$ space, the attenuation intensity of the yield ratio with the thickness of the proton skin decreases. Therefore, it is necessary to account for the effects of SRC and the neutron skin in $k$ space when deducing an isotope's proton skin thickness from other known neutron-deficient isotopes. Furthermore, we find that the surface properties of a nucleus as a projectile can be perfectly reflected by its $N/Z$ dependence of the $R(n/p)$ in the gas phase at projectile-like midrapidity. Hence, it is a helpful observable to study the surface properties of neutron-deficient nuclei near the $\ensuremath{\beta}$-stability line.