Properties of the First 1/2+ Excitation State of 13C by 22MeV Proton Inelastic Scattering

The differential cross sections of 22 MeV proton inelastic scattering for the first 1/2+ excitation state (Ex =3.09 MeV) of 13C have been measured between 9°and 130°. The broad peak located at～120°, which has beensystematically observed in the 0+ → 0-, 1/2- + 1/2+, and 1+ → 1- transitions for the 16O, 13C, and 14,15N (p, n)charge exchange reactions at Ep = 35 MeV, has been observed for the first time in the present proton inelasticscattering. The present experimental data are analysed by using microscopic distorted-wave Born approximation.From the comparison of present experimental data and theoretical results at forward angles, our analysis indicatesthe existence of neutron halo in the first 1/2+ excitation state of the 13C nucleus. In addition, by reasonablemodification of shell model wavefunction of the first 1/2+ excitation state, we can well describe the experimentalform factors of (e, e') and the experimental differential cross sections of (p, p') at incident energy of 547 Me V.