The isobar-doorway model for pion-nucleus interaction is extended to coherent ${\pi }^0$ photoproduction. The modifications to the transition operator due to many-body effects are shown to be the same as those in the optical potential. Nonlocality associated with isobar propagation, recoil corrections, and an off-shell extrapolation of the $\pi N\Delta$ vertex are included. The calculated cross sections are found to be in good agreement with the existing data.

NUCLEAR REACTIONS Coherent ${\pi }^0$ photoproduction; isobar doorway; optical potential model. Many-body modifications of the transition operator.

• Received 1 July 1980

DOI:https://doi.org/10.1103/PhysRevC.23.351