C12(p,pn)C11Cross Section from Threshold to 340 Mev

The excitation function for the reaction ${\mathrm{C}}^{12}\mathrm{}(p,pn)\mathrm{}{\mathrm{C}}^{11}$ has been measured from threshold to 340 Mev using the Berkeley 40-ft linear accelerator and 184-in. cyclotron. Absolute cross-section measurements were made at various energies, using a Faraday cup and calibrated beta-counter. The threshold occurs at 18.5±0.3 Mev. The cross section has a broad maximum of 100 millibarns near 45 Mev and decreases to 43 millibarns at 340 Mev.