The experimental excitation function of the 23ZTh (p,?,)z33pa reaction in the proton energy range 7-20 MeV was analysed within the direct-semidirect model. It was found that the confinement of the direct transition matrix element integral to the surface of the nucleus improves the fit of the theoretical curve to the experimental data. This conclusion was strenghtened by the calculations carried out for the 176yb(p, ~)177Lu experimental reaction cross sections, available from the literature.
PACS: 25.40.LW