Lower energy photon cross sections near atomic shell edges

Photon attenuation cross sections have been measured from time to time using radioactive isotopes as photon sources in various geometries. There are, however, inconsistencies between the measured values and the available tabulated values of attenuation coefficients based on different theoretical models. The measured values are particularly deficient for photon energies in the neighbourhood of the K-shell binding energies of attenuator elements. With the objective of filling such gaps in the experimental data as well as improving the data of earlier measurements, we have undertaken the present measurements in the energy region 43–1330 KeV. The measurements are made with the transmission technique using a NaI detector in the "good geometry," in which no gamma-ray photon scattered from the absorber at an angle greater than 0.3° can reach the detector. Results covering the elements from Z = 6–92 are presented and compared with the tabulated values of Hubbell et al. and Schaupp et al.