Hard X-ray photon-in photon-out spectroscopy

X-ray absorption spectroscopy (XAS) has become an indispensable tool in catalysis research. The instrumentation at synchrotron radiation sources as well as analysis and calculation of XAS has reached such a high level that this technique is now attractive to a very large user community. Standard XAS, however, cannot answer all questions and complementary techniques that address the electronic structure in more detail and help to investigate low Z elements as ligand or absorber add to the repertoire of hard X-ray techniques. We discuss in this contribution how energy analysis of the scattered photons [1] in addition to control of the incident photon energy (cf. Figure 1) extends the range of applications of XAS and addresses some problems that XAS cannot solve [2].