The angular distribution for the ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$($\gamma$,$n_0$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction was observed in the energy region 6.5 to 9.3 MeV and at angles of 90° and 135°. The photoneutron measurements were analyzed in terms of a multilevel $R$-matrix formalism. The ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$($n$,$n$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ reaction channel was explicitly included in this analysis. The effects of potential capture were directly observed in the photoneutron spectra. The ground-state radiative widths for resonances in this energy region were deduced from the $R$-matrix interpretation of the results. The ground-state transition probabilities for $E1$ excitations at 7.69 and 8.19 MeV were found to be in good agreement with the predictions of the weak-coupling model.

NUCLEAR REACTIONS ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$($\gamma$,$n_0$)${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, $E_{\mathrm{exc}}=6.5-9.3\mathrm{}$ MeV, measured $\sigma \left(\theta \right)$, $\theta =90\mathrm{}°, 135°$; deduced ${\Gamma }_{\gamma 0}$.

• Received 26 November 1979

DOI:https://doi.org/10.1103/PhysRevC.21.1699