Total Electron Compton Cross Section at 319 Mev

The total cross section for Compton scattering of 319-Mev photons by electrons was measured in an indirect manner to be 2.8±{}0.4 mb per electron. This result is 8% smaller than the theoretical cross section given by the Klein-Nishina formula, but agrees within the experimental error.The data also yield the triplet-production cross section for beryllium, which was found to be 36.0±{}3.5 mb per beryllium atom. The theoretical value is 30.2 mb per beryllium atom.The total-absorption cross sections for 319-Mev photons in beryllium and lead were found to be 161.3±{}1.0 mb per beryllium atom and (37.620±{}0.225)×{}10^-24 cm² per lead atom. The ratio of the pair-forming cross sections in beryllium to those in lead, for 319-Mev photons, was found to be (3.986±{}0.020)×{}10^-3.The deviation from experiment of the Bethe-Heitler theory for pair production can be expressed by φₚᶻ=φₚᶻ(B.H.)[1-aZ²], and a value a=(1.50±0.08)×10^-5 is derived from the measured absorption cross section for lead.Tables of the principal photon interaction cross sections in beryllium at 319 Mev are included.