# Resonant scattering

The elementary theory of the scattering of X-rays by atoms, leading to the real atomic scattering factor *f*_{o}, applies only for X-radiation whose

.

The real and imaginary terms, , in the atomic scattering factor are independent of sin(θ)/λ and in *f*_{o}. The values of and change most at the absorption edge of the element in question.

In the older literature the term *anomalous dispersion* was used for resonant scattering. In macromolecular crystallography the term *anomalous scattering* is used widely in place of resonant scattering.

### History

The resonant scattering of X-rays was theoretically predicted by Waller (Waller, I., 1928, *Über eine verallgemeinerte Streuungsformel*. *Z. Phys.* **51**, 213-231.) and first calculated by Hönl (Hönl, H., 1933, *Zur Dispersionstheorie der Röntgenstrahlen*. *Z. Phys.* **84**, 1-16; Hönl, H., 1933, *Atomfactor für Röntgenstrahlen als Problem der Dispersionstheorie (K-Schale)*.

*Ann. Phys.*(Leipzig),

**18**, 625-657.