Proton halo or skin in the excited states of light nuclei

Properties of nuclei N-13,N-15 and B-9 are investigated in the relativistic mean-field theory with NLZ and NL3 force parameters. The calculated binding energies are very close to the experimental ones. The calculations show that the first excited state (1p(1/2)) in B-9, the first excited state (2s(1/2)) in N-13 and the second excited state (2s(1/2)) in N-15 are weakly bound. In particular, for N-13 and N-15, the proton density distributions in the two above excited states have a long tail and the rms radii of the last proton are greatly larger compared with their respective matter radii. It is predicted that a proton halo exists in the first excited state of N-13 and in the second excited state of N-15, respectively. It also indicates that the first excited state in B-9 is a proton skin state.