Thresholds and mechanisms in electron-stimulated desorption of ions and neutrals from covalent adsorbates on metals

Abstract

Electron energy dependences of ionic and neutral electron-stimulated-desorption yields have been measured for covalently bonded adsorbates. Valence excitation is shown to be one primary mechanism for all cases. Core ionization with subsequent Auger decay, resulting in multiple-valence ionization, is clearly seen as primary mechanism for ionic desorption only, and only for adsorbate core levels. Neutral desorption has absolute thresholds lower than ions and additional structure at ionic valence thresholds, but not at core thresholds.