CarbonKVVAuger line shapes of graphite and stage-one cesium and lithium intercalated graphite

Abstract

A symmetry-resolved one-electron density of states (DOS) for graphite is extracted from existent x-ray photoelectron and x-ray emission spectroscopy (XES) data and used in conjunction with empirical atomic matrix elements to construct a carbon $\mathrm{KVV}$ Auger line shape for graphite which is in substantial agreement with experiment. For the intercalated graphites, an additional peak is added to the graphite one-electron DOS near the Fermi energy. In the absence of available XES data for ${\mathrm{C}}_{8}$Cs and ${\mathrm{C}}_{6}$Li, the energy and intensity of this peak are determined by fitting the C $\mathrm{KVV}$ Auger spectra. The enhanced intensities found for this peak, relative to the ultraviolet photoelectron spectroscopy data, are interpreted as being due to the screening charge surrounding the C $1s$ core. The measure of this enhancement corresponds to 0.5 and 0.6 electrons (intercalant charge donation plus screening) on the core-ionized carbon atom for the case of ${\mathrm{C}}_{8}$Cs and ${\mathrm{C}}_{6}$Li, respectively. No evidence is found for the selection rule or large matrix-element effects postulated in previous work.