Results of a measurement of the π−p charge-exchange process at backward angles are presented. Differential cross sections were measured in the angular region −0.5<cosθ*<−1.0 at incident momenta of 2, 3, 4, 5, and 6 GeV/c. An additional background subtraction to a version of the data published previously has a significant effect at 6 GeV/c and brings the data into agreement with more recent measurements. The 6-GeV/c data were combined with existing measurements of the differential cross sections for backward π+p and π−p elastic scattering to yield values for the isotopic-spin-½ and −32 u-channel and s-channel amplitudes for backward pion-nucleon scattering and for the magnitude of the phases between them. It is found that the u-channel amplitudes can be explained by pure Regge-pole (Δδ, Nα) exchange only near the extreme backward direction, but that a Reggeized absorption model agrees at least qualitatively with the data. The phase difference between the I=12 and 32 s-channel amplitudes is approximately 90° over the region −0.8<u<0 (GeV/c)2.
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