Cluster structures observed in 40Ca from 12C+28Si scattering

We discuss evidences of strong cluster structures observed in nuclear reactions even at quite high excitation energies. The oscillatory angular distributions of the elastic scattering of the 12C+28Si system measured at 13 energies close to the Coulomb barrier were reproduced introducing in the scattering S-matrix additional Regge-pole form terms. These poles were interpreted as describing doorway states with 12C+28Si cluster structure in the composite nucleus 40Ca. The excitation energies of these states indicate that they can be part of a rotational band in 40Ca, together with similar states observed in the elastic scattering and α-transfer reactions of the 16O+24Mg system. We propose that the presently observed, largely deformed molecular band corresponds to the hyper-deformed band in 40Ca, which has been found in a new Nilsson-model-calculation, which predicts preference of the 12C + 28Si and 16O + 24Mg molecular structures, in accordance with our present results.