We have measured the ratio of the cross section for gamma + n --> pi0 + n to the cross section for gamma + p --> pi0 + p at 4.7 and 8.2 GeV. The measurements were made by detecting the recoil nucleons in coincidence with the decay gamma rays of the pi0's produced from a deuterium target. At 4.7 GeV the cross-section ratio, R= sigma ( gamma + n --> pi0 + n) / sigma ( gamma + p --> pi0 + p), is less than 1.0 at low t, with an indication of a dip at about t=-0.7(GeV / c)^2, and rises to 1.0 at high t. The ratios at the higher energy have less structure and are uniformly closer to 1.0.
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including erratum: Phys. Rev. Lett. 30, 814 (1972)
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