The scattering of 8.0 and 9.0 MeV neutrons by 27Al, 28Si, 31P and 32S

Abstract

Measurements were made of the differential elastic and inelastic cross sections for neutrons scattered by silicon at 7.71 MeV; and aluminium, silicon, phosphorus and sulphur at 7.97 and 9.05 MeV. Natural scattering samples were used. Finite sample corrections were made for the elastic scattering data. The elastic cross sections have rms relative and absolute uncertainties of 2–5 % and 6–8 % respectively. The inelastic cross sections have rms relative and absolute uncertainties of 3–8 % and 6–10 % respectively. All measured elastic cross sections were compared to theoretical calculations obtained by adding the shape elastic contribution from the optical model to the compound elastic contribution from the statistical model with level-width-fluctuation corrections. Theoretical calculations of the inelastic scattering from the first excited states of 28Si and 32S were made by summing the statistical and direct interaction predictions. The measurements agree with the models for 32S. For 28Si, only the 9.05 MeV measurements were in agreement with the models. The particle-core coupling model was used to compute the direct interaction contributions to the inelastic cross sections of the low-lying levels of 27Al and 31P. These predictions do not adequately describe the inelastic scattering of neutrons by 27Al and 31P.