THEORY OF PARTICLE-INDUCED KINETIC ELECTRON-EMISSION FROM SIMPLE METALS - COMPARATIVE-STUDIES OF DIFFERENT EXCITATION AND SCATTERING MECHANISMS FOR AL, MG, AND BE

The characteristics of electron emission induced by charged particle beams (electrons, ions) can be calculated from first principles only for simple metals. The microscopic description of the particle-induced kinetic electron emission based on the transport equation formalism allows the investigation of different excitation and scattering mechanisms which govern the electron emission of these metals. Besides the excitation of single conduction and inner shell electrons, the indirect excitation of conduction electrons by plasmon decay and Auger processes is taken into account. Results of detailed calculations for Mg and Be will be presented using the same basic models as in the case of Al. An extended range of impact energies for electron and proton bombardment is considered. Depending on the impact energy, some statements obtained for Al concerning the relative importance of different excitation mechanisms have to be modified for Mg and Be. Special attention is devoted to the electron emission related to the excitation of conduction electrons via interband transitions by decay of bulk plasmons generated by the impinging particle. It is shown that for both emission phenomena this excitation mechanism is of importance in the whole range of impact energies. In the case of proton-induced kinetic electron emission it can be shown that at proton impact energies slightly above the threshold for plasmon generation there is a direct relation between plasmon dispersion and the energetic position of the so-called plasmon shoulder in the energy distribution of emerging electrons.