Line shape of the AgM4,5VVAuger spectra measured by Auger-photoelectron coincidence spectroscopy

Abstract

We present high resolution Ag ${M}_{5}\mathrm{VV}$ and ${M}_{4}\mathrm{VV}$ Auger spectra obtained in coincidence with ${3d}_{5/2}$ and ${3d}_{3/2}$ core photoelectrons, respectively. Auger photoelectron coincidence spectroscopy (APECS) was used to separate these overlapping Auger lines and determine the intrinsic line shape of each spectrum. As the on-site Coulomb correlation energy U of Ag is comparable to twice the $4d$ bandwidth, $2W,$ (i.e., $U/2W\ensuremath{\sim}1),$ the coincidence Auger spectra exhibit both atomiclike and bandlike character. We find that whether considered separately or in combination, neither bandlike nor atomiclike line shapes give a satisfactory account of these Auger spectra. Instead, the intrinsic Ag ${M}_{5}\mathrm{VV}$ and ${M}_{4}\mathrm{VV}$ line shapes are well described by the Cini-Sawatzky theory when it is applied separately to each component of the multiplet structure of the ${4d}^{8}{5s}^{2}$ Auger final state. A fit to the APECS data indicates that the correlation energy the ${}^{1}{G}_{4}$ multiplet is $4.8\ifmmode\pm\else\textpm\fi{}0.1\mathrm{eV}.$ Furthermore, our analysis indicates that the missing intensity in the vicinity of the ${}^{3}{F}_{4}$ multiplet in the Ag ${M}_{5}\mathrm{VV}$ Auger line, which has been noted in previous studies, results from a shift in the spectral weight of this multiplet component to higher kinetic energy, into the bandlike region of the spectrum.