The Scattering of X-Rays from Gases

Intensity of the scattering of molybdenum x-rays from carbon dioxide, argon, oxygen, nitrogen, helium, and hydrogen at scattering angles from 20° to 155°.—All except hydrogen show excess scattering (with helium it may, however, be due to nitrogen present as an impurity): the excess scattering extends to larger angles from the primary beam as the atomic number of the gas increases and as the wave-length increases. This excess scattering appears to be mostly, if not wholly, due to interference arising within the atom. Destructive interference is prominent with argon, and seems probable (though it is very weak) with oxygen, carbon dioxide, and nitrogen. Mark and Schocken's results, which indicated scattering by gases follows the ($1+{cos}^2\theta$) law, are not confirmed. Hydrogen follows within experimental error the quantum theory prediction of Breit, Dirac, Gordon, and Waller. Even when the $K_{\alpha }$ rays of molybdenum are used the scattering from hydrogen does not show the irregularities predicted by Debye's interference theory.