INVESTIGATION OF FUSION L-DISTRIBUTIONS AT NEAR AND SUBBARRIER ENERGIES THROUGH FISSION FRAGMENT GAMMA-RAY MULTIPLICITY MEASUREMENTS

Measurements of fission fragment gamma ray multiplicity distributions were carried out at near and subbarrier energies in C-12, O-16 + Th-23 2 reactions. The results were analyzed to determine the average values of the total fragment spin, which were used to deduce the average spi n of the compound nucleus [l](CN). It is observed that [l](CN) decreas es smoothly with decreasing bombarding energy and saturates as the ene rgy falls through the barrier, thereby resembling features analogous t o those predicted by various fusion models. The present results do not indicate any anomalous feature in the [l](CN) at the sub-barrier ener gies, which imply that the recently observed anomalous fragment anisot ropies in these systems are not due to anomalous broadening of fusion l distributions but may result from the narrowing of K distribution in the fission process.