Multiple scattering approach for two-electron resonant emission studied by angle-resolved coincidence spectroscopy RID G-2497-2011 RID G-7348-2011

We have developed a generalization of the multiple-scattering formalism to deal with Auger-photoelectron coincidence spectroscopy (APECS) in the solid state. We have merged the exact atomic treatment of the angular correlations between the two electrons and the single-particle approach, on which the multiple-scattering description of condensed matter relies. This allows the recovering, even in extended systems, of the entangled form of the electron-pair wave function characterizing the coincidence angular diffraction pattern. In the atomic limit our formalism correctly reproduces the cross section, as calculated within the statistical-tensors approach, usually employed in atomic physics. We have then performed numerical calculations for the Ge(100) L(3)M(45)M(45) APECS and compared the results with previous experiments. We found that, in the given geometry, the diffraction patterns in coincidence with different directions of the photoelectron keep little memory of the atomic anisotropy. We speculate on the conditions to be fulfilled in order to enhance the atomic-orbital sensitivity in APECS through solid-state diffraction effects