Towards a prediction of fission cross sections on the basis of microscopic nuclear inputs

Recently, a sound description of some of the basic nuclear ingredients required in the calculation of fission cross sections has been obtained. These concern in particular fission barriers within the Hartree-Fock-Bogoliubov (HFB) method and nuclear level densities at the fission saddle points within the combinatorial model. Both ingredients are determined coherently, the nuclear level densities being estimated on the basis of the single-particle scheme and pairing strength of the same mean field model that was used to determine the fission saddle points. The aim of the present study is to evaluate the quality of such inputs in the calculation of fission cross sections. Although the barrier height can still not be predicted with an accuracy better than about 700 keV, the use of the full HFB fission path and the corresponding WKB calculation of the probability to penetrate the fission barrier clearly provides a better way to estimate fission cross section in comparison with highly parametrized phenomenological models, when no experimental data is available. It is shown that a satisfactory estimate of the fission cross section for nonenergy applications can be achieved with a global renormalization of the barrier height and the microscopic nuclear level densities at the fission saddle points. Good agreement with experimental data can be obtained if both the fission barrier heights and level densities are independently renormalized. The resulting barrier heights required to reproduce experimental cross sections are found to be smaller by a few hundred keV with respect to previous analyses.