ENERGY-MOMENTUM DENSITY OF GRAPHITE BY (E,2E) SPECTROSCOPY

The energy-resolved electron momentum density of graphite has been mea sured along a series of well-defined directions using (e,2e) spectrosc opy. This is the first measurement of this kind, to our knowledge, per formed on a single-crystal target with a thoroughly controlled orienta tion which clearly demonstrates the different nature of the sigma and pi bands in graphite. Good agreement between the calculated density an d the measured one is found, further establishing the fact that (e,2e) spectroscopy yields more direct and complete information on the valen ce electronic structure than any other method.