Observation of unfilled electron states in alkali graphite intercalation compounds by secondary electron spectroscopy

The energy position of distinct σ-electron energy bands above the Fermi level has been measured in pure graphite, in a variety of stage 1 alkali intercalation compounds and in several stages of C_xK. Changes of the σ-band gap between occupied and unoccupied states near the Λ-point by a nonuniform shift of the valence- and conduction-bands are small for the heavy alkali graphite intercalation compounds, whereas a change of 1 eV is observed for C₆Li.