Photoelectron spectroscopy with hard X-rays

The use of hard X-ray synchrotron radiation as the primary excitation for photoelectron spectroscopy has recently attracted great interest. At HASYLAB, a dedicated instrument for experiments in the photon energy range 2.3-10 keV (electron energies up to 7.5 keV) has been in operation for several years. The overall energy resolution is source limited to about 0.4 eV, which is well suited for most core level studies. Scientific work using this instrument has so far focused on the near-threshold excitation of inner-shell Auger transitions and the electronic properties of buried structures and interfaces. Here, general aspects of photoelectron spectroscopy using X-rays in the keV energy regime are discussed and some applications are presented.