A new high-energy (e, 2e) spectrometer for the study of the electronic structures of materials

Full text: Electron momentum spectroscopy (also called (e,2e) spectroscopy) is a very direct method of studying the electronic structure of materials. Using only the elemental laws of energy and momentum conservation this spectroscopy measures the probability that an electron in a target has a binding energy E and momentum q. However, the measurement is only valid if the (e,2e) event is the only scattering event during the experiment. Multiple scattering (plasmon creation and elastic scattering) is a severe problem at low energies. On the other hand, the cross section for the (e,2e) event is small at high energies. An (e,2e) spectrometer was constructed at the ANU that works at high energies, but still has a good count rate. It uses 50 keV incoming and 25 keV outgoing electrons. A set of spectra can be obtained in 24 hours. The first results show that the energy-resolved momentum densities stand out clearly, superimposed on only a small multiple scattering background