Systematic Analysis of Fission Cross Sections of Actinides by means of Double-Humped Barrier Model

Abstract

Neutron-induced fission cross sections of 24 actinide nuclei were analyzed in terms of the double-humped fission barrier model to deduce the barrier heights. Good fits were obtained by assuming that the first barrier is mass-symmetric and axially asymmetric, while the second barrier is mass-asymmetric and axially symmetric. Systematic trends were observed in the barrier heights of the actinide nuclei ; the first barrier height as a function of neutron number tends to be peaked at N ?? 147, whereas the second barrier height increases linearly as a function of (1-χ)³ A ^2/3, where χ is the fissility. By decomposing the barrier heights into liquid-drop and shell correction parts, the surface energy coefficient was deduced to be 17.55 MeV. This value is consistent with existing values obtained from nuclear mass system-atics. This fact corroborates the theoretical conjecture that the shell correction is damped at larger deformation corresponding to the second barrier. Near constancy of the fission barrier heights for actinides (fission barrier anomaly) was interpreted in terms of the three-component analysis.