Backangle anomaly in scattering of α -particles from 28 Si at low energies Original Research Article

In order to resolve the differences in the literature on the existence of quasi-molecular states in the α -28 Si system, excitation functions were measured for the scattering of α -particles from 28 Si in the incident energy range View the MathML source –7.8 MeV. An angular distribution measurement was carried out in the angular range View the MathML source –174.5 ° for every potential resonance observed in the excitation functions. Data was analysed using a Regge-pole formalism by coherently adding specific resonances to an underlying diffraction term calculated by a strong absorption model. Furthermore, the usual compound elastic contribution was incoherently added to the direct interaction part of the cross section. The 6.8 MeV resonance was confirmed with J=3 and some evidence was observed for a J=1 resonance around 6.0 MeV.