Anomalous anisotropies of fission fragments for sub-barrier fusion-fission reactions

It is shown that preequilibrium fission can give rise to a large anisotropy at sub-barrier energies for the ¹⁶O{+}²³²$Th and $¹²C+²³⁶U reactions, since the transmission coefficient is several times larger for target orientation angles around 180^∘{} in comparison with angles around 90^∘{}. At higher energies the effect dilutes, since the transition probability becomes of approximately equal magnitude for all orientations.