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Incoherent Scattering of Gamma Rays from the Bound Electrons of Heavy Elements

1957; IOP Publishing; Volume: 70; Issue: 5 Linguagem: Inglês

10.1088/0370-1298/70/5/304

1747-3829

J. Randles,

Advanced X-ray and CT Imaging

In the experimental study of the coherent (elastic) scattering of gamma rays of energy greater than 1 MeV from the electrons of heavy atoms, the energy resolution of the available detecting instruments makes it impossible to distinguish between photons scattered coherently and those scattered incoherently with an energy loss of up to about 10%. The experimental results therefore include an unknown amount of incoherent scattering, the contribution of which is calculated in this paper. The answer is stated as the ratio of incoherent to coherent cross sections which is observed with a detector with the type of response to radiation assumed in the text, and the derivation is valid for large angles (≳ 60°) and the energies of interest (≃ 1 MeV). Since the method of solution is much clearer in non-relativistic quantum mechanics, we have presented the necessary details within this framework and outlined at the end the procedure for the more exact relativistic theory. As will be seen, the ratio of the cross sections for tin is given well by the non-relativistic approximation although the absolute cross section is not. For heavier elements (e.g. mercury), only the relativistic theory is acceptable.