New measurements of coherent and incoherent photon scattering by low, medium and high Z atoms

Coherent and incoherent photon scattering by bound electrons in low, medium and high Z atoms, over energies of 0.145-1.33 MeV and scattering angles below 15 degrees (momentum-transfer range 0-0.4 mc) and from 15 degrees to 150 degrees (0.1-4.0 mc), have been investigated experimentally. The results of the authors' relatively high precision measurements have also been compared with the predictions of new theoretical calculations for bound-electron incoherent and coherent scattering in the incoherent scattering-factor and form-factor approximations and for the Rayleigh and Delbruck scattering amplitudes over a high momentum-transfer range, to give a critical verification of the theory. It was found that for 0.145 MeV photons scattered with low momentum transfer, the F(q,Z) formalism is valid for low and medium Z atoms but not for the high Z (Z=82) atom. At all energies and in the low momentum-transfer range studied in the present work, the S(q,Z) formalism was found to be adequate for bound-electron incoherent scattering for all the atoms.