Modeling of High-Precision Neutron Nonelastic Cross Sections

Abstract

A new method has been applied to the determination of neutron nonelastic cross sections for iron 56 Fe and lead 208 Pb for energies between 5 and 26MeV. These data have estimated errors of only a few percent and do not suffer from the ambiguities encountered in earlier nonelastic data. We attempt to fit these high precision data using both a semiclassical single phase shift model (nuclear Ramsauer model) as well as a recent global optical model that well reproduces a wide body of neutron scattering observables. At the 5% uncertainty level, both models produce satisfactory fits. However, neither model gives satisfactory fits to these new precise data. We conclude that fitting precise data, i.e., data with errors of approximately 2% or less, may require a nuclear mass dependence of radii that reflects structure effects such as shell closures.

On the accuracy of techniques for determining neutron compound-nucleus formation cross sections

“…We give a brief description of this technique, which has been developed and applied to several cases ( 208 Pb, 54,56 Fe, 232 Th, and 238 U) in Refs. [8][9][10]. We define σ W 0 , the Wick's limit value for the c.m.…”

Multiband coupling and nuclear softness in optical model calculations for even-even and odd-A actinides

“…Dietrich developed a special method to obtain non-elastic cross sections[29,30] based on the optical theorem, and the measured total cross sections and corresponding elastic angular distributions.…”