Systematic analysis of inelastic α scattering off self-conjugate A=4n nuclei

We systematically measured the differential cross sections of inelastic α scattering off self-conjugate A=4n nuclei at two incident energies Eα=130MeV and 386MeV at Research Center for Nuclear Physics, Osaka University. The measured cross sections were analyzed by the distorted-wave Born-approximation (DWBA) calculation using the single-folding potentials, which are obtained by folding macroscopic transition densities with the phenomenological αN interaction. The DWBA calculation with the density-dependent αN interaction systematically overestimates the cross sections for the ΔL=0 transitions. However, the DWBA calculation using the density-independent αN interaction reasonably well describes all the transitions with ΔL=0-4. We examined uncertainties in the present DWBA calculation stemming from the macroscopic transition densities, distorting potentials, phenomenological αN interaction, and coupled channel effects in C12. It was found that the DWBA calculation is not sensitive to details of the transition densities nor the distorting potentials, and the phenomenological density-independent αN interaction gives reasonable results. The coupled-channel effects are negligibly small for the 21+ and 31- states in C12, but not for the 02+ state. However, the DWBA calculation using the density-independent interaction at Eα=386MeV is still reasonable even for the 02+ state. We concluded that the macroscopic DWBA calculations using the density-independent interaction are reliably applicable to the analysis of inelastic α scattering at Eα∼100MeV/u.