Inelastic Scattering of 14-Mev Neutrons from Carbon and Beryllium

The angular distributions of the neutrons from the reactions Be⁹(n, n^')Be9*, Q=-2.43 Mev, and C¹²(n, n^')C12*, Q=-4.43 Mev, have been measured from 25^∘{} to 140^∘{}, employing 14-Mev incident neutrons. Neither distribution is symmetric about 90^∘{}; the inelastically scattered neutrons are peaked in the forward direction. The C¹²(n, n^') first-level angular distribution, which agrees with a recent measurement of the C¹²(p, p^') distribution, is in good agreement with the prediction of the Levinson-Banerjee direct interaction theory. The integrated inelastic scattering cross sections for the Be⁹ and C¹² first levels are 0.17±{}0.03 barn and 0.22±{}0.03 barn, respectively.The 4.43-Mev de-excitation gamma rays from C12* are symmetric about 90^∘{}. The gamma-ray production cross section at 90^∘{} is 13.1±{}2.0 mb/sterad. No gamma rays associated with Be9* 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 Be⁹.