Grazing Incidence Diffraction Anomalous Fine Structure in the Study of Structural Properties of Nanostructures

Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques

“…Once established, the concepts of XAFS have influenced and given birth to other related techniques, such as X-ray magnetic circular dichroism (XMCD), ,,,,− diffraction anomalous fine structure (DAFS), ,,,− photoelectron diffraction, − various electron energy-loss techniques, including extended energy-loss fine structure (EXELFS) − and extended fine Auger structure, − β-decay near threshold (or beta environmental fine structure BEFS), extended appearance potential fine structure, photon interference XAFS (PIXAFS), , and the related X-ray ̀holography’ effects . The basic physic in all of these techniques involves similar high-order electron-atom multiple-scattering processes, which can all be treated with theoretical tools similar to those developed to understand XAFS spectroscopy …”

Determination of the electronic and structural configuration of coordination compounds by synchrotron-radiation techniques

“…Tuning the incident wavelength in the closest proximities of the edge (resonant conditions), the incident X-ray photons can interact with the bound inner electrons of the correspondent atom, be absorbed, and give photoelectric effect. Importantly , the anomalous effects near an absorption edge for an atom contained in the sample, selectively enhance the contribution of that atom to the elastically scattered intensity [138,228,230,[544][545][546]. This phenomenon can be exploited in a variety of cases.…”

“…Interestingly, the measurements on the whole series pointed out that the extent of cation exchange at Mn 2+ sites is significantly influenced by the identity of the substituent metal. As anticipated, among the structural techniques based on anomalous scattering, we have DAFS [89,546,573,574]. Although DAFS so far has been scarcely applied to coordination compounds, a brief discussion of this method is deserved, considering its foreseeable diffusion in the close future and its analogies with XAS.…”

“…From DANES, in some favourable cases, it can be possible to distinguish the presence of atoms of the same element in different oxidation states in a specific crystallographic site (valence-difference contrast method [557,[575][576][577]). In addition, EDAFS spectra combine long-range information from diffraction and elementally-selective local sensitivity equivalent to that provided by EXAFS, enabling site-and chemical-selective structural characterization [546,573,574]. On the experimental ground, EDAFS collection is very demanding.…”

“…It is worth noting that the EDAFS signal contains contributions from both the real, Δf' (λ), and imaginary, Δf " (λ), parts of the complex anomalous scattering factor, whereas EXAFS signal is proportional only to the imaginary part. Nevertheless, an EXAFS-like analysis procedure has been successfully applied to EDAFS spectra [546,578]. The technique is commonly applied, also in combination with EXAFS, in the structural determination of complex nanostructural materials, where amorphous and crystalline phases coexist [579] (e.g.…”