ABSTRACT
When X-rays penetrate into matter, a number of photon-atom interactions may occur, the probability of each process being given by its cross section. The cross sections depend on the energy of the X-rays and the specic element under investigation, and their sum is dened as the total absorption coefcient. For elements with Z > 10 and in the X-ray energy range from several to few tens of keV (very often dened as the hard X-ray regime), the photoelectric effect is the most dominant process.1-3 In a single photon bound-electron interaction, the core electron may be excited to higher unoccupied electronic states of an atom, or ejected into the continuum. The probability of each process depends on the energy of incident X-rays as well as on the target element in the sample. Thanks to this correspondence, element specic studies employing hard X-rays as a probe are possible. In the present chapter we focus rst on recent developments and experimental results achieved recently with different X-ray spectroscopy techniques and by employing hard X-rays in order to study and
3.1 Introduction .................................................................................................... 59 3.2 Resonant X-ray Emission Spectroscopy .........................................................60
