Proton Halo or Skin in the Excited States of Light Nuclei

Properties of nuclei ^13,15N and ⁹B 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 ⁹B, the first excited state (2s_1/2) in ¹³N and the second excited state (2s_1/2) in ¹⁵N are weakly bound. In particular for ¹³N and ¹⁵N, 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 ¹³N and in the second excited state of ¹⁵N, respectively. It also indicates that the first excited state in ⁹B is a proton skin state.