Mechanism of α-particle scattering from 28Si nuclei

Statistical and Regge pole analyses were performed on excitation functions and angular distributions for α-particle scattering on 28Si leading to the ground, 2+ (1.78)MeV and 4+ (4.62 MeV) states in the energy range 21-28 MeV. The direct interaction contribution ysub(D) for the reaction studied was determined. Angular cross-correlation coefficients (a.c.c.c.) were calculated in each channel for all pairs of experimental excitation functions. For the elastic channel a.c.c.c. were compared with the coefficients calculated using the excitation functions generated by the optical model. Channel cross-correlation coefficents (c.c.c.c) were also calculated in the full angular range for pairs of excitation functions measured at the same angle (lab). The single Regge pole model was used to describe the behaviour of the angular distribution at backward angles in the elastic channel. The l = 10 value of angular momentum for energies greater than 24 MeV was clearly distinguished. The results of the analysis indicate that at backward angles of scattering a mechanism different from the direct and compound ones contributes significantly to the reaction. (Auth.)