Elastic Scattering of Neutrons from Carbon and Oxygen in the Energy Range 3.0 to 4.7 MeV

Abstract

The elastic scattering of neutrons from oxygen and carbon was studied in the neutron bombarding energy range 3.0 to 4.7 MeV. Angular distributions were obtained by the method of recoiling gas atoms in a proportional counter. Data were taken over the entire energy range in approximately 250-keV intervals, and in smaller intervals near certain resonances. Differential cross sections for $\mathrm{C}\mathrm{}(n,n)\mathrm{}\mathrm{C}$ were obtained relative to the total $n-p$ cross section. Similarly, $\mathrm{O}\mathrm{}(n,n)\mathrm{}\mathrm{O}$ differential cross sections as well as the ${\mathrm{O}}^{16}(n,\alpha ){\mathrm{C}}^{13}$ total cross section were determined relative to the derived $\mathrm{C}\mathrm{}(n,n)\mathrm{}\mathrm{C}$ cross sections. A phase-shift search routine was used to find acceptable least-squares fits to a Legendre-polynomial decomposition of the elastic-scattering results. Energy-level parameters were obtained for five states in ${\mathrm{O}}^{17}$ and are given as follows (in the order: resonance energy relative to the ${\mathrm{O}}^{17}$ ground state in MeV, spin and parity, and dimensionless reduced width): $7.24({\frac{3}{2}}^{+},0.15)$, $7.69({\frac{3}{2}}^{-},0.07)$, $7.70({\frac{7}{2}}^{-},<\mathrm{}0.03)$, $7.83({\frac{1}{2}}^{-},0.04)$, and $8.07({\frac{3}{2}}^{-},0.02)$. Level parameters were also determined for two states in ${\mathrm{C}}^{13}$: $8.27({\frac{3}{2}}^{+},0.45)$ and 8.87 (${\mathrm{½}}^{-}$, 0.03).