Introduction to Electron Momentum Spectroscopy

Abstract

Electron momentum spectroscopy (EMS) measures the energy-momentum density of electrons in atoms, molecules, and solids by means of a kinematically complete ionization reaction initiated by an electron beam. Electronic states of the ion are resolved by the experiment. The differential cross section for ionization at sufficiently high energy, scanned over the difference between the initial and total final electron momenta and energies, beginning near zero, is very sensitive to the energy-momentum density. The total energy is sufficiently high if the structure information is insensitive to large energy increases. The experimental conditions may be arranged so that the difference of the total initial and final electron momenta can be identified with the momentum of the initially bound electron, and the probability of observing it is proportional to the energy-momentum density.