Total Photoelectric Cross Sections of Copper, Molybdenum, Silver, Tantalum, and Gold at 662 kev

The total photoelectric cross sections of copper, molybdenum, silver, tantalum, and gold have been measured at 662 kev. A highly collimated beam of gammas from a Cs-137 source impinged upon a thin disk of a target material. Photoelectrons from a target were detected by a plastic scintillator subtending very nearly $4\pi$ steradians. Pulse-height analysis permitted partial resolution of photoelectric and Compton events. After subtraction of unresolved Compton events and correction for coherent scattering effects, the cross sections were found to be 0.125±0.009, 0.700±0.016, 1.198±0.028, 8.55±0.14, and 11.62±0.16 barns, respectively, in satisfactory agreement with theory.