X-ray absorption spectroscopy (XAS) is used to investigate the valence electron configuration in intermetallic compounds and other phases because energy, amplitude and shape of energy rich absorption lines depend on the valence state of the investigated element.(XANES). Additionally, modulation e.g. fine structure of the spectra close to the absorption edge contains information on the local environment of the absorbing atom (EXAFS).

In case of rare earth metals the occupation of an additional 4f state leads to smaller absorption energies which differs by ca 8 eV for the L3 absorption lines. For this reason, spectra of mixed valente compounds show two contributions close to the absorption edge which can be attributed to both electronic configuration of the rare earth metal. In many cases it is possible to investigate the influence of the parameter pressure, chemical composition and temperature on the mixed valente electronic configuration of the rare earth element by means of X-ray absorption spectroscopy (s. figures).

Most of our activities in this field with energy rich radiation (> ca. 3.5 keV) are realised at the Hamburger Synchrotron Laboratory (HASYLAB). The method XAS is applied for the systematic characterisation of rare earth metal and transition metal in phases related to the following projets:
- Borides
- Carbometallates
- Nitrides
- RE Chalkogenborates
- Skutterudites.