AUTOIONIZATION OF ADSORBATES

A number of autoionization spectra of adsorbates are presented ranging from weak to strong adsorbate-substrate interaction. Spectra of CO chemisorbed on different substrates and in different adsorption sites are shown. The dynamical aspects of the core hole decay are illustrated from an extensive series of spectra recorded at different photon energies for CO and N2 on Ni(100). The differences in autoionization spectra from chemisorbed and physisorbed systems are discussed for Ar adsorbed on silver and graphite surfaces. For N2 on graphite, vibrationally selective excitation provides a tool to study the vibrational dependent autoionization process. Furthermore, excitations to higher states leads to complicated autoionization and Auger spectra depending on whether the intermediate states are neutralized by a charge transfer from the substrate or remain ionized when the core hole decays.