Relativistic mean-field study on proton skins and proton halos in exotic nuclei

We investigate the ground state properties of proton-rich nuclei in the fra mework of the relativistic mean-field model. Calculations show that the exp erimental proton halo in the nuclei P-26,P-27,P-28 can be reproduced by the model. The proton halos can appear in proton-rich nuclei because the total nuclear potential is attractive up to the radial distance r approximate to 5.5 fm. But the size of proton halos is finite due to the limitation of th e Coulomb potential barrier. The mean-square radius of a halo proton is not very sensitive to the separation energy of the last proton in some very pr oton-rich nuclei due to the effect of the Coulomb barrier. This behavior is different from the case of a neutron halo where the mean-square radius of a halo neutron is inversely proportional to the separation energy of the la st halo neutron. We have also analysed the differences of the relativistic mean-field potentials of Al-25 and P-26 and found that the isovector potent ial from the rho meson has an important effect on the differences. (C) 1999 Elsevier Science B.V. All rights reserved.