Angular distributions for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\mathrm{n},{\gamma }_0){}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ reaction have been measured with neutrons corresponding to excitation energies of 16.0, 19.2, 20.1, 20.8, and 21.8 MeV. Legendre polynomial coefficients have been determined to second order ($a_3$ is small). Polarized neutron measurements were obtained at excitation energies of 16.0, 18.6, 19.2, 20.1, 21.0, 21.8, and 22.3 MeV. A structure seen in the coefficient of the Legendre polynomial $P_2$ for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\mathrm{p},{\gamma }_0){}_{}{}^{13}{}_{}{}^{}\mathrm{N}$ reaction is also seen in the present data. A secondary doorway state at 20.5 MeV with an apparent width of 0.5 MeV is suggested by previously measured ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}(\mathrm{d},{\gamma }_0){}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ data. The presence of this state provides an explanation for the energy dependence of the cross section, the $a_2$ coefficient, and the analyzing power coefficient $b_2$ in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\mathrm{n},{\gamma }_0){}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ data. The same model is also able to describe the energy dependence of the cross section and the $a_2$ coefficient observed in the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}(\mathrm{p},{\gamma }_0){}_{}{}^{13}{}_{}{}^{}\mathrm{N}$ reaction in the region of 16 to 22 MeV.

• Received 9 November 1983

DOI:https://doi.org/10.1103/PhysRevC.29.1186