Photoionization studies of surface layers. Electron spectroscopy and ion desorption

By virtue of the continuous tunability, high resolution at good intensities, and well-defined polarization of synchrotron radiation, photoionization processes of surface species - as monitored by photoelectrons, Auger electrons and fragment ions - can be investigated in much greater detail than with line sources. Information about the composition of these species, their geometry (orientation, interatomic distances), their electronic structure and bonding, and many-particle processes in them can be derived from electron spectroscopies. The strong screening of photoholes in surface species, in particular on metals, has the consequence that mainly multiple excitations stay localized sufficiently long for ion desorption to occur. Thus photodesorption is a selective, localized probe. As an example for the application of synchrotron radiation to surface physics, it is shown that correlation of results of electron spectroscopies and of ion yields leads to an improved understanding of all the processes involved.