Photon-absorption cross sections between 3 and 30 MeV

Photon absorption by Al, Ta, and Bi between 3 and 30 MeV was measured using as a photon spectrometer a photoneutron time-of-flight detector and a liquid deuterium target. The atomic cross sections of Ta and Bi at the lowest energies (and of Al at higher energies) agree with calculated values appearing in published tabulations but exceed them at 25 MeV by about 2% in Ta and 3% in Bi. Calculations by others using empirical Coulomb corrections and improved screening corrections to the cross section for pair production by the nucleus agree with experiment to within (0.5\ifmmode\pm\else\textpm\fi{}0.4)%. Best experimental values of the combined correction for Bi are given.