The lowering of the Fermi energy in stage-1 Fe${\mathrm{Cl}}_3$-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.

• Received 15 February 1979

DOI:https://doi.org/10.1103/PhysRevLett.43.68