Differential cross-sections of the elastic and inelastic 13C + α scattering were measured at E(α) = 90 MeV. The root mean-square radii
(< Rrms >) of 13C nucleus in the states: 8.86 (1/2−), 3.09 (1/2+) and
9.90 (3/2−) MeV were determined by the Modified diffraction model
(MDM). The radii of the first two levels are enhanced compared to
that of the ground state of 13C, confirming the suggestion that the
8.86 MeV state is an analogue of the Hoyle state in 12C and the 3.09
MeV state has a neutron halo. Some indications to the abnormally
small size of the 9.90 MeV state were obtained.
