Deformed Halo of ^{29}_{9}F_{20}

Abstract

Using a simple model based on the knowledge of spherical and deformed Woods-Saxon potentials, it is shown that the recent observation of halo phenomena in 29 F can be interpreted as an evidence for the prolate deformation of the ground state of 29 F. The prolate deformation is the result of the shell structure, which is unique in one-neutron resonant levels, in particular near degeneracy of the neutron 1f 7/2 and 2p 3/2 resonant levels, together with the strong preference of prolate shape by the proton number Z = 9. On the other hand, in oxygen isotopes spherical shape is so much favored by the proton number Z = 8 that the presence of possible neutron shell-structure may not make the system deformed. Thus, the strong preference of particular shape by the proton numbers 8 and 9, respectively, together with a considerable amount of the energy difference between the neutron 1d 3/2 and 2s 1/2 orbits in oxygen isotopes seems to play an important role in the phenomena of oxygen neutron drip line anomaly, as was suggested by H. Sakurai et al. in 1999.