Resolution of the anomalous fission fragment anisotropies for the 16O+208Pb reaction.

Abstract

Fission and evaporation residue cross sections and fission fragment angular distributions have been measured for the reaction $^{16}\mathrm{O}$${+}^{208}$Pb in small energy steps spanning the barrier region. Fission fragment anisotropies have been calculated using the transition state model, making use of spin distributions more accurately determined from the new cross-section data, and a more realistic calculation of the nuclear temperatures at the saddle point. Comparison of these calculations with the new experimental anisotropies show no evidence for anomalously large fission fragment anisotropies at beam energies below the average fusion barrier. Thus, the standard models of fusion and fission are able to describe the new data.