Inelastic Scattering of 14-Mev Neutrons from Carbon and Beryllium

Abstract

The angular distributions of the neutrons from the reactions ${\mathrm{Be}}^{9}(n, {n}^{\ensuremath{'}}){\mathrm{Be}}^{9*}$, $Q=\ensuremath{-}2.43$ Mev, and ${\mathrm{C}}^{12}(n, {n}^{\ensuremath{'}}){\mathrm{C}}^{12*}$, $Q=\ensuremath{-}4.43$ Mev, have been measured from 25\ifmmode^\circ\else\textdegree\fi{} to 140\ifmmode^\circ\else\textdegree\fi{}, employing 14-Mev incident neutrons. Neither distribution is symmetric about 90\ifmmode^\circ\else\textdegree\fi{}; the inelastically scattered neutrons are peaked in the forward direction. The ${\mathrm{C}}^{12}(n, {n}^{\ensuremath{'}})$ first-level angular distribution, which agrees with a recent measurement of the ${\mathrm{C}}^{12}(p, {p}^{\ensuremath{'}})$ distribution, is in good agreement with the prediction of the Levinson-Banerjee direct interaction theory. The integrated inelastic scattering cross sections for the ${\mathrm{Be}}^{9}$ and ${\mathrm{C}}^{12}$ first levels are 0.17\ifmmode\pm\else\textpm\fi{}0.03 barn and 0.22\ifmmode\pm\else\textpm\fi{}0.03 barn, respectively.The 4.43-Mev de-excitation gamma rays from ${\mathrm{C}}^{12*}$ are symmetric about 90\ifmmode^\circ\else\textdegree\fi{}. The gamma-ray production cross section at 90\ifmmode^\circ\else\textdegree\fi{} is 13.1\ifmmode\pm\else\textpm\fi{}2.0 mb/sterad. No gamma rays associated with ${\mathrm{Be}}^{9*}$ are seen. It is concluded that about one-third of the ($n, 2n$) cross section at 14 Mev is a two-stage process proceeding via the 2.43-Mev level in ${\mathrm{Be}}^{9}$.