A systematic study of mass yield curves in proton-induced fission of actinides

Proton-induced fission was studied for 233U, 237Np, and 239Pu targets. Mass yield curves and excitation functions of fission fragments were obtained in the proton energy range of 9-16 MeV for 233U, and 9-32 MeV for 237Np, 9-16 MeV for 239Pu. It was found that the excitation functions of symmetrically divided fission fragments were quite different in shapes and threshold energies from those of asymmetrically divided ones. For understanding of these experimental results, the observed cross sections and the ratios of symmetric and asymmetric products were analyzed by a statistical model. The differences in the symmetric and asymmetric fission barriers were compared with those of the theoretical calculation by Moller et al. (author)