FISSION FOLLOWING COMPLETE OR INCOMPLETE FUSION OF 135 MEV O-16 AND U-238

From measurements of the laboratory angular distribution and the projected range distribution for each of 26 individual radioactive fission products from the interaction of 135 MeV O-16 on U-238, we have determined for each product quantities including the average velocity, v, of the parent fissioning system and the anisotropy, omega, of the fission angular distribution. We have interpreted the results in terms of two competing mechanisms: complete fusion and a process involving transfer of an alpha-particle from projectile to target followed by fission of Pu242. The values of v lie between v(cn), the complete fusion value, and 0.3 v(cn), and can be taken as a measure of the relative importance of the two processes competing in populating each observed product. These two contributions to each measured product yield can then be separated, and understood using a simple model of the fission process. The data suggest that approximately 24% of the overall fission yield is due to incomplete fusion processes. The anisotropy, omega, is strongly correlated with the value of v, indicating anisotropies of 1.4 and 2.8 for the two individual processes.