Effect of Thermal Vibrations on Diffraction from Perfect Crystals. I. The Case of Anomalous Transmission

The temperature behavior of anomalously diffracted x rays in thick crystals (${\mu }_{0}t=20\mathrm{}$) of germanium has been experimentally determined. The behavior is consistent with a Debye-Waller factor of $\exp \mathrm{}(-1.32M)\mathrm{}$ which, from the present state of the theory is unexpected. Theory suggests $e^{-M}$. The possibility of explaining this behavior in terms of a thermally vibrating standing wave field is presented. The absolute value of the imaginary part of the scattering factor for a nonvibrating atom has been experimentally determined for several reflections. The experiment indicates that this quantity is sensibly independent of angle which is is disagreement with a classical treatment of anomalous dispersion. The possibility of explaining these results by a more refined calculation is discussed.