We examine how the Pauli exclusion principle affects the pion-nucleus optical potential U in the region of the ${\Delta }_{33}$ resonance, i.e., for pion kinetic energies of 50–300 MeV. In our formulation the exchange effects enter through n-body correlation functions and contribute to U as higher-order corrections in a density expansion. We study the rate of convergence of the expansion and derive an integral equation that sums selected exchange terms to all orders. We calculate the isoscalar, isovector, and isotensor components of U for the cases of infinite nuclear matter and finite nuclei. We identify the limiting conditions under which our treatment of the Pauli effect reduces to that in more familiar approaches.

• Received 16 April 1985

DOI:https://doi.org/10.1103/PhysRevC.32.531