X-ray emission studies of adsorbates

X-ray emission spectroscopy applied to adsorbate systems is shown to reveal new details of the chemical bond formed at surfaces. An atom and symmetry projected view of the bonding orbitals is obtained. We will present recent studies of atomic C, N and O adsorbed on Ni(100) and Cu(100). The differences in bonding on Cu and Ni surfaces can be related to the concept of less or more noble metals. For the molecular adsorbed CO and N-2 on Ni(100) we can also distinguish the distribution of the electronic states between the two different atoms within the adsorbate. New types of molecular states are observed which are directly related to the surface chemical bond. Furthermore, to obtain a complete picture it is also important to consider changes in the whole molecular framework. (C) 1998 Elsevier Science B.V. All rights reserved.