Fermi-Level Lowering and the Core Exciton Spectrum of Intercalated Graphite

The lowering of the Fermi energy in stage-1 FeCl₃-intercalated graphite is directly measured in the spectrum of electronic excitations from carbon $1s$ core states to empty carbon $2p$ states which appear after intercalation. The shape of the core exciton spectrum is related to the initial distribution of empty states in a formulation of the core exciton problem which includes the effect of electronic relaxation near the core hole.