Systematic study of anomalous fragment anisotropies in subbarrier complete fusion—fission reactions

The complete fusion-fission is separated from the transter-induced-fission with the fragment folding angle technique.The cross sections and fragment angular distributions for the complete fusion-fission reactions of 11B 238U(237Np),237NP,16O 232Th(238U) and 19F 232Th at near-and sub-barrier energies have been measured.The present fusion and fission standard models can reproduces both the excitation functions and the fragment anisotropies for the systems of 11B 238U(237Np)and 12C 237Np;but fail to explain both the experimental data for the other 3 systems simultaneously,The evidence of the entrance-channel dependence of fission-fragment anisotropies is revealsed by comparison of the 11B 237NP and ^16O 232Th data.Based on the observations a new version model of preequilibrium fission is put forward to explain the anomaly.

Systematic study of anomalous fragment anisotropies in subbarrier complete fusion fission reactions

The complete fusion fission is separated from the transfer induced fission with the fragment folding angle technique. The cross sections and fragment angular distributions for the complete fusion fission reactions of 11 B 238 U( 237 Np), 12 C 237 Np, 16 O 232 Th( 238 U) and 19 F 232 Th at near and sub barrier energies have been measured.The present fusion and fission standard models can reproduce both the excitation functions and the fragment anisotropies for the systems of 11 B 238 U( 237 Np) and 12 C 237 Np; but fail to explain both the experimental data for the other 3 systems simultaneously. The evidence of the entrance channel dependence of fission fragment anisotropies is revealed by comparison of the 11 B 237 Np and 16 O 232 Th data. Based on the observations, a new version model of preequilibrium fission is put forward to explain the anomaly.