Multiple-scattering approach with complex potential in the interpretation of electron and photon spectroscopies

We present a unitary cluster approach to the calculation of several electron and photon spectroscopies, ranging from core and valence level photoelectron diffraction and absorption to electron, Auger and anomalous diffraction. Electron energy loss and Auger-photoelectron coincidence spectroscopies can also be treated in the same frame. This approach is based on multiple-scattering theory with a complex optical potential of the Hedin-Lundqvist type and is valid for all electron kinetic energies. Similarities and differences between these diffraction techniques are examined and cluster size convergence is discussed in connection with the electron mean free path. Applications to selected problems are presented to illustrate the method, both for structural and electronic analysis. (topical review)