The formalism for calculating the radiative pion capture cross section has been developed for shell model calculations in the impulse approximation. It includes the momentum dependent terms of the effective transition operator for any angular momentum of the pion. The giant dipole and giant quadrupole resonances are discussed. The quasifree background is calculated within the framework of the distorted wave impulse approximation. Realistic shell model calculations for ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ yield good agreement with experiment.

NUCLEAR REACTIONS Theory of ${\pi }^{-}$ capture. Shell model, impulse approximation. Giant dipole and quadrupole states of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$. Quasifree background.

• Received 14 April 1975

DOI:https://doi.org/10.1103/PhysRevC.12.1278