Abstract
The fission cross sections and fragment angular distributions for the complete fusion-fission reactions of 11B + 238U, 237Np, 12C + 237Np, 16O + 232Th, 238U, and 19F + 232Th at near-and sub-barrier energies have been measured by the fragment folding angle technique. It is revealed that the anomalous anisotropies of fission fragments in latter three systems are existence. Based on the experimental observations and Dφssing and Randrup's theory, a new version model of preequilibrium fission is put forward to explain the anomaly.
