Antineutrons produced by 440-Mev antiprotons incident upon Pb, C, and C${\mathrm{H}}_2$ targets have been observed. The antineutrons were detected by their energy release upon annihilation. Charge-exchange cross sections for antiprotons in the three targets have been calculated. The results show that the effective charge-exchange cross section per proton of the target nucleus decreases rapidly with increasing $Z$.

• Received 26 August 1957

DOI:https://doi.org/10.1103/PhysRev.108.1557