Fourier transform absorption fine structure

Figure 8.39 Fourier transformed Fe extended X-ray absorption fine structure (EXAFS) and retransformation, after applying a 0.9-3.5 A filter window, of (a) a rubredoxin, (b) a plant ferredoxin and (c) a bacterial ferredoxin, whose structures are also shown. (Reproduced, with permission, Ifom Teo, B. K. and Joy, D. C. (Eds), EXAFS Spectroscopy, p. 15, Plenum, New York, 1981)...

In the present study, we synthesized in zeolite cavities Co-Mo binary sulfide clusters by using Co and Mo carbonyls and characterized the clusters by extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and high resolution electron microscopy (HREM). The mechanism of catalytic synergy generation in HDS is discussed. 

Final justification for using terms such as inner- or outer-sphere awaits direct spectroscopic confirmation. Electron Spin Resonance, Mossbauer, and Fourier Transform Infrared-Cylindrical Internal Reflection Spectroscopic techniques are being used to establish the structure of surface complexes (see, e.g., McBride, Ambe et al., and Zeltner et al., this volume). The potential for using EXAFS (extended x-ray absorption fine structure) to establish the type of surface complex for Pb + adsorbing onto goethite is currently being undertaken in our laboratory. 

Table 5.2 Summary of selected analytical methods for molecular environmental geochemistry. AAS Atomic absorption spectroscopy AFM Atomic force microscopy (also known as SFM) CT Computerized tomography EDS Energy dispersive spectrometry. EELS Electron energy loss spectroscopy EM Electron microscopy EPR Electron paramagnetic resonance (also known as ESR) ESR Electron spin resonance (also known as EPR) EXAFS Extended X-ray absorption fine structure FUR Fourier transform infrared FIR-TEM Fligh-resolution transmission electron microscopy ICP-AES Inductively-coupled plasma atomic emission spectrometry ICP-MS Inductively-coupled plasma mass spectrometry. Reproduced by permission of American Geophysical Union. O Day PA (1999) Molecular environmental geochemistry. Rev Geophysics 37 249-274. Copyright 1999 American Geophysical Union...

Using various amines added to the ammonia bath (in most cases with added hydrazine), sphalerite ZnS fihns were obtained with a crystal size of ca. 3 nm [ 118]. Rutherford Backscattering Spectroscopy (RBS) analyses showed that there was about twice as much Zn in the fihns as S. (More basic solution and more hydrazine gave more stoichiometric films). Extended X-ray Absorption Fine Structure (EX-AFS) and Fourier Transform Infra-red (EUR) spectroscopy showed that the fihns did not have Zn-0 groups but rather Zn-OH ones [122] and that there is probably a mixture of ZnS and unreacted Zn(OH)2, quite likely as a ZnS shell around a Zn(OH)2 core. Optical spectra gave a bandgap of ca. 3.85 eV, considerably blue-shifted from the bulk value of 3.6 eV, as expected from such small crystals. 

The term 1 or h indicates low or high coverage of adsorbed ethene, as inferred from ethene exposures.h TPD, temperature-programmed desorption LITD, laser-induced thermal desorption 1 FT-MS, Fourier-transform mass spectrometry SIMS, secondary-ion mass spectrometry MS, mass spectrometry T-NEXAFS, transient near-edge X-ray absorption fine structure spectroscopy RAIRS, reflection-absorption infrared spectroscopy. d Data for perdeut-erio species.1 Estimated value. 

First qualitative analyses of the Fourier transformations (FTs) of the respective EXAFS (extended X-ray absorption fine structure) oscillations of the reference compounds (figure 6) show peaks up to 5.5 A while the incorporated transition metal oxides A and B show only peaks up to 3.3 A. A comparison of the first shell (oxygen shell) between 1 and 2 A shows no difference in the magnitude for the reference CoFe2C>4 and the products A and B. In contrast, the higher shells, which represent the metal-metal distances, are strongly reduced for the products A and B compared to the bulk reference compounds, which is another indication for small particles within the pores. Further quantitative EXAFS analyses are currently in progress. 

Although they may be part of a catalyst testing [1-3] programme, investigations focused on revealing the reaction mechanism, such as in-situ Fourier transform infrared (FTIR) in transmission or reflection mode, nuclear magnetic resonance (NMR), X-ray diffraction (XRD), X-ray absorption fine-structure spectroscopy (EXAFS), X-ray photoelectron spectroscopy (XPS), electron microscopy (EM), electron spin resonance (ESR), and UV-visible (UV-vis) and the reaction cells used are not included. For the correct interpretation of the results, however, this chapter may also provide a worthwhile guide. 

Particle diameter Inductively coupled plasma-optical emission spectrometry (ICP-OES) Fourier transform infrared spectrometry Mass spectrometry X-ray fluorescence Extended X-ray absorption fine structure (EXAFS) spectroscopy X-ray absorption near edge (XANES) spectroscopy Static and dynamic laser light scattering Scanning probe technologies... 

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