Interaction cross sections for Ne isotopes towards the island of inversion and halo structures of 29Ne and 31Ne

Interaction cross sections (σI) for Ne isotopes from the stability line to the vicinity of the neutron drip line have been measured at around 240 MeV/nucleon using BigRIPS at RIBF, RIKEN. The σI for 27-32Ne in every case exceed the systematic mass-number dependence of σI for stable nuclei, which can be explained by considering the nuclear deformation. In particular the σI for 29Ne and 31Ne are significantly greater than those of their neighboring nuclides. These enhancements of σI for 29Ne and 31Ne cannot be explained by a single-particle model calculation under the assumption that the valence neutron of 29Ne (31Ne) occupies the 0d3/2 (0f7/2) orbital, as expected from the standard spherical shell ordering. The present data suggest an s dominant halo structure of 29Ne and s- or p-orbital halo in 31Ne.