Consistent description of collective level structure and neutron interaction data for ¹²C in the framework of the soft-rotator model

We have measured the neutron elastic and inelastic scattering angular distributions of ¹²C at 28.2 MeV. This data, together with information from other works, was used to construct a neutron scattering data-base in the energy region from 20 to 40 MeV. Then, a systematic analysis of nuclear structure and neutron interaction data for ¹²C was carried out in the framework of the soft-rotator model. The model was firstly applied to analyse the low-lying collective level structure of the ¹²C nucleus successfully. The intrinsic wave function obtained in such an analysis was then used to construct the coupling potentials in the coupled-channels formalism to calculate the neutron total and scattering cross sections. The quadrupole deformation parameter obtained in the present analysis was 0.164, which was much smaller in the absolute sense than the value used in the rotation-vibration model employed frequently in the past, i.e. ≈0.6. When averaged over the β-vibration function, however, the present result yields an effective quadrupole strength of about the same scale as the previous studies due to softness of the ¹²C wave function with respect to β² degree of freedom. The soft-rotator model was found to be very successful in reproducing both the structure and neutron scattering data consistently for the first time in this mass region.