Fine-structured spectra

Although there are no examples of wrell-resolved fine-structure spectra for surface complexes, polycrystaliine spectra for bulk species have been... 

Fine structure spectra obtained at the X-ray X-absorption edge of an element are not yet completely resolved theoretically or experimentally. However it appears that this branch of spectroscopy even now may be of aid to catalyst research. Meaningful spectra of elements of the first transition series, even in concentrations sometimes as low as i%, can be readily obtained this is also true in conditions inaccessible by diffraction... 

Haschke et al. (2000) have demonstrated the occurrence of a superoxide Pu02+JC(s) that reportedly formed between 25 and 350 C and contained Pu(VI). Runde et al. (2002) reported XAS evidence for the existence of Pu(V) instead of Pu(VI). Fine structure analysis for the Pu solid precipitated at 90 °C in a Yucca Mountain groundwater was compared with data for a Pu02(S) standard. The measured Pu-O distance of 0.185 nm is characteristic for Pu(V) and agrees well with the measured Pu-O bond distance of the Pu(V)02(aq) ion at 0.181 nm. The Pu-O bonds in hexavalent Pu compounds are much shorter. Other details in the X-ray absorption fine structure spectra supported the assignment of Pu as Pu(V). At ambient temperatures, oxidation of Pu(IV) was extremely slow and formation of Pu(V) was not observed. 

Urquhart, S. G., and Ade, H. (2002). Trends in the carbonyl core (C IS, O IS) —> pi C=0 transition in the near-edge X-ray absorption fine structure spectra of organic molecules. 

X-Rav Absorption Fine Structure. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure spectra (EXAFS) were obtained for a series of Sn/Pt on alumina or silica samples (45,46). The data suggest the possibility of Pt/Sn alloy formation, but do not provide conclusive proof for this. 

The results for the bulk centers in the alkaline-earth oxides show that, in principle, EPR spectra could be obtained for a pair of O" ions separated by R on the surface. However, there are no examples of well-resolved fine-structure spectra for such adsorbed species. The main reasons for this are expected to be as follows From the above formula, one would anticipate the spacings between the lines in the parallel and parpendicular directions to increase with decreasing distance R. It is therefore likely that with the heterogeneity of sites that has been discussed previously for isolated O species, the EPR spectrum would be difficult to observe. Electrostatic repulsion will favor the collinear orientation of the two trapped holes on opposite sides of the positive ion vacancy, as observed from the relaxation... 

Most recently in theoretical approaches to the analysis of NO spectra, Varberg, Stroh and Evenson [133] have used their tunable far-infrared measurements, described in chapter 10, to refine, yet again, the values of the constants. Using results from the A-doublet, rotational and fine-structure spectra of 14NO (v = 0) which have been recorded, the following values of the constants (in MHz) are listed [133] ... 

X Ray edge and extended absorption fine structure spectra of zinc at the active site are consistent with a seven-coordinate or distorted octahedral environment/ Analysis of the fine structure eliminates sulfur ligands and suggests Zn—N or Zn—O distances of 2.04 and 2.10 A. These are appropriate for an octahedral complex. There is evidence for atoms at distances of 3-4 A from... 

The EXAFS (Extended X-ray Absorption Fine Structure) spectra of the residues were analyzed and the Fourier transforms for pure FeS2 and Fe Sg are shown in Figure 9. The Fourier transforms of the EXAFS spectra after reaction are shown in Figure 10. The first prominent peak in all the spectra is due to Fe-S distances (2.26 A for FeS2 and 2.44 X for Fe Sg). The second peak is due to the iron next-nearest neighbor—one for pyrite, but more complicated for FCySg since there are many iron distances present. For the residues of the reactions with FeS2 present, the Fourier transform is dominated by the Fe-S distance Fe-Fe distances are difficult to identify. This is attributed to the fact that the iron atoms and vacancies in the Fe. S structure (atomic % iron = 47.8) are extremely disordered and randomly distributed, in marked contrast to the residues of the reaction in the presence of Fe Sg. In the... 

M. Winterer, Reverse Monte Carlo analysis of extended x-ray absorption fine structure spectra of monoclinic and amorphous zirconia, J. Appl. Phys. 88(10), 5635-5644... 

In Table 5.9 some numerical values for the atomic spin-spin parameter are reported, calculated, or deduced from fitting of atomic fine-structure spectra. These values are only a few hundredths of reciprocal centimeters for atoms heavier than first-row atoms. 

Urquhart S, Ade H, Rafailovich M, Sokolov JS, Zhang Y (2000) Chemical and vibronic effects in the high-resolution near-edge X-ray absorption fine structure spectra of polystyrene isotopomers. Chem Phys Lett 322 412-418... 

Urquhart SG, Ade HW (2002) Trends in the carbonyl core (C Is, Is) to n transition in the near edge X-ray absorption fine structure spectra of organic molecules. JPhys Chem 106 8531-8538 Vairavamurthy A, Manowitz B, Zhou W, Jeon Y (1994) Determination of hydrogen sulfide oxidation products by sulfur -edge X-ray absorption near edge structure spectroscopy. In Environmental Geochemistry of Sulfide Oxidation. Alpers CN, Blowes DW (eds) Am Chem Soc Symp Series, Vol 550, Am Chem Soc, Washington, DC, p 412-430... 

ESR spectra of powdered [VOCl2(Ph3P)2] show some fine structure. " Spectra for VOC12... 

Francesco RD, Stener M, Fronzoni G (2012) Theoretical study of near-edge X-ray absorption fine structure spectra of metal phthalocyanines at C andN K-edges. J Phys Chem A 116 2285-22894... 

Near-Edge X-Ray Absorption Fine-Structure Spectra... 

As already mentioned in Section 2.3, molecules show complex and fine-structured spectra. This is due to the numerous rotational, vibrational and electronic transitions possible between the different energy levels. While the first two types of transitions are present in the microwave to IR region, the electronic ones mostly lie in the visible to UV wavelength range and therefore are the dominant causes of spectral interference with atomic lines or erroneous background correction (BC). 

Linares M, Stafstrom S, Rinkevicius Z, Agren H, Norman P. Complex Polarization Propagator Approach in the Restricted Open-Shell, Self-Consistent Field Approximation The Near K-Edge X-ray Absorption Fine Structure Spectra of Allyl and Copper Phthalocyanine. J Phys Chem B. 2010 115 5096-5102. 

Cor] XRD, EXAFS (X-ray absorption fine structure) spectra, XPS (X-ray photoelectron spectroscopy) Fe37Coi7Bi503i, T— 200, 350, 450, 550°C... 

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