Double-humped barrier effects in the R-matrix for fitting of fissile isotope

Abstract

The Reich--Moore approach has been extensively used in the resolved resonance energy range (RRR) for a wide range of isotopes. The approximation was suggested for cross-section representation of fissile isotopes since experimental fission width distribution according to given resonance spin and parity showed that only a few degrees of freedom (DoF) was involved during the fission process. Experimental cross-section data in RRR were successfully reproduced, and the interference in fission channels were well described. The fitting of the fission cross-section data was done according to one or two fission channels for a given resonance spin (J) and parity (π). Using the two-fission channel representation, channel interference effects observed on cross-section data for fissile heavy isotopes were adequately treated but only on a phenomenological basis. Indeed, this approach is physically unsatisfactory since no fission penetrability is involved in reduced fission channel width evaluation, and therefore no actual connection between R-matrix fission channel widths and Aage Bohr transition fission channels can be made neither in terms of individual barrier height or by the shape. This paper intends to address model deficiency by including ‘fluctuating’ fission barrier penetrability as a function of resonance spin and parity.