First principles calculation of ion induced kinetic electron emission fromnearly free-electron metals below the plasmon threshold

The excitation of electrons by decay of plasmons generated directly during the interaction of the impinging particle with the system of conduction ele ctrons of the metal results in an important contribution to the electron em ission at higher impact energies. However, also below the so-called plasmon threshold (nearly 40 keV for proton impact on Al), when a direct excitatio n of plasmons is impossible, several experimental investigations show a rem arkable contribution of kinetic excitation of plasmons. Starting from first principles, a theoretical description of the plasmon excitation during the electron capture process as well as by fast secondary electrons generated by binary ion electron collisions is given. Explicit calculations were perf ormed for proton impact on Al. (C) 2000 Elsevier Science B.V. All rights re served.