Angular distributions of the neutron polarization for the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha , n_0){}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and ${}_{}{}^9{}_{}{}^{}\mathrm{Be}(\alpha , n_1){}_{}{}^{12}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}$ (4.43-MeV) reactions have been measured at six projectile energies in the 4.5- to 5.85-MeV interval. Large polarizations are observed for both neutron groups over the whole energy range, making both groups useful sources of polarized neutrons. The ground-state neutronpolarization angular distributions have been analyzed simultaneously with the recent cross-section data of Obst et al. using an $S$-matrix search code to make $J^{\pi }$ assignments to states in ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ in the 13- to 15-MeV excitation energy range. The combined data set can be adequately described over the whole energy range by assuming the presence of at least five broad states. The $J^{\pi }$ assignments and the probable excitation energies for these states are given.

• Received 22 December 1972

DOI:https://doi.org/10.1103/PhysRevC.7.1824