X-ray Absorption Spectroscopy
X-ray absorption spectroscopy (XAS) is a set of advanced techniques used for probing the local environment of matter at atomic level and its electronic structure. The experiments require access to synchrotron radiation facilities for their intense and tunable X-ray beams. Samples can be in the gas phase, solutions, or solids. Background XAS data are obtained by tuning the photon energy, using a crystalline monochromator, to a range where core electrons can be excited (0.1-100 keV). The edges are, in part, named by which core electron is excited: the principal quantum numbers n = 1, 2, and 3, correspond to the K-, L-, and M-edges, respectively. For instance, excitation of a 1s electron occurs at the metal K-edge, K-edge, while excitation of a 2s or 2p electron occurs at an metal L-edge, L-edge (Figure 1). There are three main regions found on a spectrum generated by XAS data, which are then thought of as separate spectroscopic techniques (Figure 2): # The ''absorption thresho ...
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