We measured the interaction cross-sections of light nuclei at energies of a
round 950 A MeV. We deduced effective matter radii of the nuclei by a Glaub
er-model analysis. Based on the assumption of a core + neutron structure, w
e have applied the Glauber-model analysis for few-body system to odd-N nucl
ei in C and O isotopes. As the byproduct, we deduced the effective nucleon
matter densities to reproduce the observed sigma (I) and the one-neutron se
paration energies for halo nuclei. One-neutron halo structure is suggested
for O-23.