Electron scattering spectroscopy

Abstract

In electron scattering spectroscopy, atomic and molecular energy levels are studied by accurate measurement of the flux of non-relativistic energy-monochromated electrons scattered in angle with analysed energy loss. The measurements are expressed using the Bethe and Born approximations in terms of generalized oscillator strengths, which can be calculated from known wave-functions, and which serve as a sensitive test of the quality of wave-functions. Total as well as differential crsss-sections are useful in this respect. Energy loss spectra can also be measured at the threshold of excitation. Low impact energy (1–20 eV) spectra show up the existence of resonances, or compound states of electron and atom or molecule, appearing as structure in the cross-section functions. Spectroscopic constants and assignments of these resonances can be obtained from differential cross-sections for excitation of available channels. The electric and magnetic deflection techniques for the high-resolution momentum monochromation and analysis of non-relativistic electrons are also discussed.