C12(n, α)Be9Reaction Induced by 14-MeV Neutrons

The reaction has been studied with emulsions. Total cross section for the forward hemisphere (lab) and first 5-MeV excitation is 144±57 mb, of which 62±15 mb is associated with the ground-state group. These are consistent with earlier estimates, and with measured values for the inverse process. Angular distributions of the ground and 2.4-MeV excited state groups have the direct interaction form, and a spin of $\frac{3}{2}$ is indicated for the excited state. This value supports earlier arguments for $\mathrm{LS}$ coupling in ${\mathrm{Be}}^9$, and suggests that the 2.4-MeV state consists of ${\mathrm{Be}}^8$ in its first excited state and a $p$-state neutron. Comparison of the ratio of reduced widths, for transitions to the 0.0- and 2.4-MeV states, with an estimate of the ratio of the corresponding coefficients of fractional parentage, favors a knockout mechanism.