Single-scattering theory of x-ray absorption

We describe an independent-particle theory of x-ray absorption in condensed matter, which is similar to extended x-ray—absorption fine-structure theory in only retaining a single backscattering from near neighbors but which properly treats the spatial variation of the scattered wavelets. This slight modification yields a good description of the relevant features of the spectra down to the absorption edge, without increasing the computational burden. This success is illustrated by a model calculation for the $K$-edge spectrum of copper.