A rapid, exact curved-wave theory for EXAFS calculations

A simplified version of the exact curved-wave theory of EXAFS is described. The simplifications arise from the angle-averaging process which is necessary when analysing data from polycrystalline or amorphous samples. Such an angle-averaging process is here performed analytically, resulting in a much simpler theoretical expression for the EXAFS function, but one which still treats the outgoing spherical wave exactly. Test runs show that such a theory is about a factor of forty faster in computation time than the original form of the curved-wave theory. Such rapid computation allows the authors routinely to use the curved-wave theory in structural analyses, rather than the plane-wave approximation which is limited to high photoelectron energies.