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Optical reflectance experiments were performed on several GAC (Br 2 , AlCl 3 , SbCl 5 -graphite) of well-defined stage ( n = 2,3,4). We observed i.r. reflectivity structures whose energies are characteristic of the stage, but depend slightly on the intercalate species. These stage-specific structures are well understood, within the framework of the model of “Graphite Independent Subsystems”, as evidence of the predicted intervalence transitions. With a charge transfer coefficient comparable with the value obtained for the lowest stages of GAC, the expected energies of the intervalence transitions are in good agreement with the experimental positions of the reflectance structures.

Optical reflectance experiments were performed on H2SO4-graphite during electrochemical synthesis. The stage formation was studied from the evolution of intervalence transitions. Quantitative analysis of the plasma reflectance spectra of pure stage compounds led to the determination of the Fermi energy as a function of the electrochemically controlled charge. The results prove the validity of the 2D band structure model and provide the first determination of the band parameter γ0 in acceptor compounds.

Optical reflectance experiments are performed on well-characterized compounds C8nAsF5 (n = 1, 2), in the temperature range 10–300 K. The theoretical analysis of the reflectivity spectra within the 2-D model of graphite independent subsystems [1] provides an optical determination of EF and the charge transfer coefficient which is found independent of temperature.