Relevance of the core hole alignment to Auger photoelectron pair angular distributions in solids

Auger-photoelectron coincidence spectroscopy (APECS) has shown that singling out Auger spectra individual components on the basis of the related photoelectron, i.e. defining the parent core ionic state, increases energy discrimination capability of both Auger and photoelectron spectroscopy. Angle resolved APECS (AR-APECS) on Ge(100) surface has shown peculiar new features of the electron pair angular distribution upon Auger detection angle. It was speculated that these features were to be ascribed to the alignment of the core-hole state induced by selection in angle of the photoelectron. Recent results on Ge(100) and Cu(111) have drawn attention on the possibility of selecting specific magnetic sublevels of both Auger and photoelectron wavefunctions. Good use of this capability has been made in singling out otherwise overlapping components of both Ge L3VV and Cu M3VV multiplet split spectra, thus demonstrating that resolution in angle improves discrimination in the energy scale as well.