Pair correlation in two-electron emission from surfaces

An electron pair emitted from a crystalline surface system is represented by a relativistic two-electron scattering state, which contains the pair correlation mediated by a screened Coulomb interaction. This state is obtained from the solutions of two one-electron Dirac equations with potentials, which incorporate the electron-electron interaction as a dynamical screening of the usual effective one-electron potentials, Numerical applications to the electron pair emission due to low-energy electron impact on a He atom and on a clean W(001) surface demonstrate that pair correlation effects can be quite strong and significantly improve the agreement of calculated results with experimental data. (C) 1999 Elsevier Science Ltd. All rights reserved.