A rapid, exact, curved-wave theory for EXAFS calculations. II. The multiple-scattering contributions

For pt.I see ibid., vol.17, p.143 (1984). The simplified version of the exact, curved-wave, single-scattering theory of EXAFS described in an earlier paper by Gurman, Binsted and Ross is here extended to the multiple-scattering contributions. The simplifications arise from using the angle-averaging process which is necessary when analysing data from polycrystalline or amorphous samples. Such an averaging over angle is here performed analytically. This results in a much simpler theoretical expression for the EXAFS function. Use of this theory shows that it is at least ten times faster computationally 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 involving strong multiple-scattering contributions rather than the plane-wave approximation whose use is limited to high photo-electron energies.