Inelastic scattering of gamma rays by K-shell electrons in heavy atoms

Abstract

The differential cross sections for the inelastic scattering of 279 keV gamma rays by K-shell electrons of bismuth are determined experimentally at six scattering angles. Two NaI(Tl) scintillation spectrometers and a fast-slow coincidence circuit are used, and the final coincidence counts are collected on a 20-channel pulse-height analyser. The bound-to-free electron differential cross section ratios are compared with those calculated using different non-relativistic theories. The experimental differential K-shell electron cross sections are compared directly with those of the free electron and with the average bound electron differential cross sections obtained on the basis of the Hartree-Fock and Thomas-Fermi atomic models. In the low-angle region the trend of the experimental differential cross section ratios agrees with that of the incoherent scattering function values based on the Thomas-Fermi model. The total cross section is also estimated and found to be a little less than 60% of that due to free electrons.