Modification of shell structure in p-sd shell nuclei studied by radioactive beams

Recent studies of interaction cross sections, fragments momentum distributions combined with standard quantities such as mass and beta-decay Q-values reveal new dynamic change of shell structures. In particular, special attention is paid on neutron halo nuclei in the p-sd shell. In halo nuclei and other neutron rich nuclei, the 2s1/2 orbital shows irregular behavior. One such extreme case is the new neutron magic number N=16. The global behavior of 2s1/2 shell is discussed in relation to the interaction cross-sections and fragment momentum distributions. Inconsistencies in understanding these data are pointed out. Peculiar changes of shells are discussed for 19C and 23O