SHAKE-UP AND SHAKE-OFF STRUCTURES IN CORE-LEVEL PHOTOEMISSION SPECTRA FROM ADSORBATES

Previous studies of the satellites in adsorbate core level spectra are reviewed. New or recently published high resolution X-ray photoemission spectra are presented. The results represent systems which cover a range of different adsorption bond strengths, from physisorption (O2/graphite) and weak chemisorption (CO/Cu(100), N2/Ni(100)) to strong chemisorption (CO/Ni(100)). The shake-up spectra reveal some new details, and are discussed in the light of previous models and interpretations. By extended shake-up/shake-off measurements, it is shown that the relative spectral weight of the main line in many cases is lower than previously suggested. The shake-up structures are discussed in terms of valence excitations in the substrate-adsorbate complex, and the role of the core hole is stressed.