Non-adiabatic electron excitation in ion-induced kinetic electron emissionfrom metal surfaces

Both high-energy features and the major low-energy peak of ion-induced kine tic electron emission spectra are often being explained by level promotion processes and by various related electron energy loss mechanisms. There are , however, many experiments, especially with very low-energy ions (hundreds of eV), where the electron promotion mechanisms cannot explain the kinetic electron emission and where the particle velocity is too low to produce el ectrons by classical particle-electron collisions. An additional mechanism for kinetic electron emission is suggested and discussed in this paper. Thi s mechanism is based on the non-adiabatic perturbation of the Fermi gas due to the rapid passage of the particle through the surface. The first quanti tative comparisons with experiments (e.g. Ne on Au) yield reasonable values for the critical microscopic parameters of the theory. (C) 2000 Elsevier S cience B.V. All rights reserved.