Electron momentum spectroscopy by asymmetric (e, 2e) collisions belonging to the Bethe ridge

Abstract

The use of the (e, 2e) technique as a tool to investigate electron momentum densities in atoms and molecules has until now been essentially confined to symmetric kinematics. Its application has often been hampered by the long time needed to perform the experiments. This work shows that asymmetric (e, 2e) events can also be described in the framework of the simple plane-wave impulse approximation even for energies of the ejected electron as low as 100 eV and intermediate incident energies (about 1500 eV), provided the kinematics belong to the Bethe ridge. The larger cross section associated with the asymmetric kinematics allows the integration time to be reduced by one order of magnitude. Electron momentum distributions of the 1s orbital of He and the 3 sigma g and 2 sigma u orbitals of N2, as determined in asymmetric kinematics, are presented, together with an estimate of the achieved reduction in integration time compared with the symmetric conditions at equal incident energy.