Direct Observation of Energy–Momentum Densities in Solids

Abstract

Electron momentum spectroscopy (EMS), based on kinematically complete observations of high energy electron impact ionisation events, directly observes energy–momentum dispersion laws and densities of electrons in solids. The valence electronic structure in the near surface region, up to a depth of about 20 Å is probed for thin free-standing films (about 100 Å) by the multiparameter EMS spectrometer at Flinders University. The principles of the measurement are described and its application to the determination of energy–momentum densities in a range of amorphous, polycrystalline and crystalline materials is discussed.