The excitation functions for the reactions ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}({\pi }^{\pm }, \pi N){}_{}{}^{11}{}_{}{}^{}\mathrm{C}$ have been measured by activation over the energy ranges 50 to 470 MeV for ${\pi }^{+}$ and 40 to 550 MeV for ${\pi }^{-}$. These excitation functions, clearly reflecting the (3,3) pion-nucleon resonance, show an upward energy shift in the resonance peak for ${\pi }^{-}$ and a downward shift for ${\pi }^{+}$. The $\frac{{\sigma }_{{\pi }^{-}}}{{\sigma }_{{\pi }^{+}}}$ ratio at 180 MeV is 1.55 ± 0.10.

• Received 6 February 1975

DOI:https://doi.org/10.1103/PhysRevLett.34.821