K-EQUILIBRATION AND SPIN ENHANCEMENT EFFECTS IN 120 MEV O-16- AND 214MEV S-32-INDUCED FISSION

The gamma-ray multiplicities (M(gamma)) of fission fragments have been investigated in a variety of O-16- and S-32-induced reactions. The de pendence of M(gamma) on target mass and excitation energy is well expl ained by a model which assumes the thermal excitation of angular momen tum bearing collective modes. As predicted by the statistical descript ion of fission fragment angular distributions, the value of M(gamma) i s found to vary with fission fragment detection angle. The observed va riation is considerably weaker than predicted by simple rigid rotation models. A large part of this discrepancy can be explained by the exci tation of collective modes. For heavy targets, sequential fission cont ributions also weaken the angular dependence of the fragment spins. Ho wever, even with these corrections, some systems still seem to exhibit a weaker angular dependence than predicted by the model calculations. Possibly this is due to a suppression of high K-states.