Band widening in graphite

The valence band width of graphite is determined with high accuracy by imag ing the momentum distribution of photoelectrons for various binding energie s. Compared to local-density-functional theory, the experimental band width (22.0 eV) is stretched by about 11%. Quasiparticle calculations, which pro perly describe electron interaction effects on the excited states of a soli d, give a width of 21.8 eV, in agreement with the experiment within the exp erimental and theoretical relative uncertainty of about 1%. The results dem onstrate the importance of including Anal-state and associated many-body ef fects into the theoretical description of the electronic structure of solid s. [S0163-1829(99)11403-6].