Polarization Dependent Resonances in Core Initiated Photon Stimulated Desorption of Ions from Chemisorbed Molecules

Abstract

The photon stimulated ion desorption off chemisorption layers on metals is very effectively initiated by adsorbate core level ionisation. It has been shown on simple covalent adsorption systems like CO and NO on transition metals [1,2] that in particular primary multielectron excitations with energies partly much above the pure core level binding energy play an important role for fragment ion desorption. This finding differs from corresponding gas phase fragmentation results. It is ascribed to the additional charge transfer interaction of the metal underlayer which may quench certain desorption channels and which is responsible for the generally lowered desorption yields because of efficient reneutralization and partly pronounced differences in cross-sectional behaviour of the fragmentation products compared to the gas phase.