A new criterion for nuclei with anomalous neutron distribution

Comparison of the difference between the neutron and proton RMS radii, Delt a RMS, calculated from the neutron skin thickness of the droplet model was made with the data obtained from the experimental total nuclear reaction cr oss section. It was found that the droplet model reproduced the Delta RMS o f normal nuclei well, but it underestimates the Delta RMS for neutron skin and neutron halo nuclei. Since the small separation energy of last one or t wo neutron is one of the most important causes of the appearance of anomalo us nuclear structure, an effective neutron skin thickness was used to disti nguish nuclei with anomalous neutron distribution from normal nuclei, which succeeds to reproduce the abnormal increase of the neutron skin thickness for the light nuclei with neutron skin or neutron halo.