Unoccupied electronic structure of graphite probed by angle-resolved photoemission spectroscopy

We report the observation of anomalous bands in graphite valence band structure in angle-resolved photoemission spectroscopy (ARPES) experiments. The photon energy dependence of these bands shows a constant kinetic energy nature. Our results are supported by the very low energy electron diffraction data reported on graphite surfaces which essentially map the unoccupied states representing the photoemission final states. This suggests that the ARPES technique is capable of probing the unoccupied electronic states governed by the secondary electron emission process, along with the occupied bands of solids.