M(3)M(45)M(45) Auger lineshape measured from the Cu(111) surface: Multiplet term selectivity in angle-resolved Auger-photoelectron coincidence spectroscopy

The capability of the recently observed dichroic effect in angle-resolved Auger-photoelectron coincidence spectroscopy (DEAR-APECS) to disentangle individual multiplet terms has been exploited to study the lineshape of the ${M}_{3}{M}_{45}{M}_{45}$ Auger spectrum measured in coincidence with the $3{p}_{3/2}$ photoelectrons from the Cu(111) surface. The relevant multiplet structure of the two hole final state is determined with an unprecedented sensitivity, including a reliable experimental estimation of the energy of the $^{1}D$ multiplet term. Spectroscopic data for the $3p$ photoemission feature are also given and energy conservation applied to the photoelectron-Auger-electron pair has been successfully used in order to quantitatively explain energy shifts in coincidence spectra. Multiple-scattering calculations prove that the DEAR-APECS effect is not destroyed by diffraction effects and a simple model which combines atomic angular distributions and electron-diffraction modulations is provided in order to obtain a detailed understanding of the multiplet energy and intensity distributions in Auger spectra.