NEAR-BARRIER FISSION OF THE SYSTEM C-12-232(TH)

The fission fragment angular distributions for the system C-12 + Th-23 2 have been measured in the energy range 0.97 < E(c.m.)/V-B < 1.22. Th e measured anisotropies have been compared with the predictions of the standard saddle point statistical model, using the second moment of t he compound nucleus spin distribution (iota(2)) deduced from a Wong mo del fit to the fission excitation function. While the measured anisotr opies agree with the standard saddle point statistical model for E(c.m .)/V-B > 1.05, they are abnormally large at lower energies. This is al so true for the existing measurements of O-16 and F-19 + Th-232 system s. Since for this system pre-equilibrium fission contributions are not expected, this anomaly indicates strong channel coupling effects lead ing to an increase in (iota(2)) at sub-barrier energies.