NEXAFS fine-structure spectra

In Figure 1, we show the Ck edge NEXAFS spectrum of DP-PPV. The character of the fine structure spectrum in the vicinity of the absorption edge provides... 

EXAFS is part of the field of X-ray absorption spectroscopy (XAS), in which a number of acronyms abound. An X-ray absorption spectrum contains EXAFS data as well as the X-ray absorption near-edge structure, XANES (alternatively called the near-edge X-ray absorption fine structure, NEXAFS). The combination of XANES (NEXAFS) and EXAFS is commonly referred to as X-ray absorption fine structure, or XAFS. In applications of EXAFS to surface science, the acronym SEXAFS, for surface-EXAFS, is used. The principles and analysis of EXAFS and SEXAFS are the same. See the article following this one for a discussion of SEXAFS and NEXAFS. 

Lithium intercalation in VeOis has been studied by Stallworth et al. ° Variable-temperature Li NMR indicated considerable mobility for Li+ in the intercalated materials. The Li NMR data were compared with ESR spectra and near-edge X-ray absorption fine structure (NEXAFS) data on the same materials, and a correlation between vanadium oxidation state (from NEXAFS data) and NMR shift was observed. The authors explained the shifts in terms of different coupling mechanisms between the and shifts. The shifts were, however, extracted from static NMR experiments, and it is possible that some of the different local environments, typically revealed in a MAS spectrum, were not seen in this study. 

The EXAFS technique has been especially useful for metalloproteins. It has often provided the first clues as to the identity of atoms (O, N, S) surrounding a metal atom and either covalently bonded to it or coordinated with it (Chapter 16). Interpretations are often difficult, and a common approach is to try to simulate the observed spectrum by calculation from a proposed structure.118 Tautomerism in crystalline Schiff bases (see Eq. 23-24) has been studied by nearedge X-ray absorption fine structure (NEXAFS) employing soft X-rays.119... 

NEXAFS — Near-edge extended X-ray absorption fine structure (spectroscopy), evaluation of the X-ray absorption spectrum around and slightly below the absorption edge, for details see - EXAFS. 

Figure 9. Experimental C Is NEXAFS spectrum of polystyrene (a), and the simulated C Is spectrum of toluene (b). The numbered peaks in (b) correspond to the transitions of different C atoms in the molecule, and spectral broadening and additional spectral features in the experimental spectrum are attributed to the vibrational fine structure. [Reprinted with permission from Elsevier Science from Urquhart et al. (2000), Fig. 3].

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