Energy-dependent separable potentials are generated by solving the inverse problem for three sets of pion-nucleon phase shifts which differ only at very high ($E_{\mathrm{c}.\mathrm{m}.\mathrm{}}>1900\mathrm{}$ MeV) energies. While the off-shell $t$ matrices thus generated have substantial differences, these effects are small for $\pi$-nucleus cross sections as calculated within the impulse approximation.

NUCLEAR REACTIONS $\pi$-nucleus elastic scattering, impulse approximation; $\pi$-nucleon off-shell models.

• Received 23 June 1975

DOI:https://doi.org/10.1103/PhysRevC.12.1962