Cross sections have been measured for the excitation of the 12.71 MeV, T=0, and 15.11 MeV, T=1, $1^{+}$ states in ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ by 50 MeV ${\pi }^{\pm }$ scattering. The cross section ratio, R=σ(12.7 MeV)/σ(15.1 MeV), was found to be 7.5±1.5 for ${\pi }^{+}$ and 6.6±1.5 for ${\pi }^{\mathrm{-}}$ at 50 MeV, giving an isospin averaged value of R=7.05±1.06. These results indicate that the anomalous behavior of R is attributable to the energy dependence of the T=1 $1^{+}$ level. The data also indicate that the impulse approximation is probably invalid at 50 MeV, contrary to the conclusions of a recent study at 65 MeV.

• Received 30 November 1987

DOI:https://doi.org/10.1103/PhysRevC.37.1347