Electron-pair creation on uranium by 10 and 20 MeV photons.

Abstract

Improved corrections for inscattering and photon regeneration were made to observed total absorption cross sections of uranium reported earlier. Electron-pair creation cross sections ${\ensuremath{\sigma}}_{K}$ for 10 and 20 MeV photons on $^{238}\mathrm{U}$ were obtained from the adjusted total cross sections. Recently published theoretical values of ${\ensuremath{\sigma}}_{K}$ at these energies agree within about 1% with the revised experimental values. The discrepancy at 10 MeV was previously thought to be about 4%. The remaining discrepancy may be due to neglect of the finite size of the nucleus in the calculations, or to slightly inaccurate screening or radiative corrections.