Ray Absorption and Mossbauer Spectroscopies

Noninvasive surface spectroscopies can be applied in the presence of liquid water most of them involve the input and detection of photons. The best known examples are nuclear magnetic resonance, electron spin resonance, Raman, Fourier transform infrared, UV-visible fluorescence, X-ray absorption, and Mossbauer spectroscopies, although Brown (28) enumerated many others that are available to detect adsorbed ions. These methods, some of which are listed in Table II along with citations of illustrative applications, can be used both noninvasively and in conjunction with in situ probes. 

Recently, however, considerable doubt has been cast on these conclusions. In the case of the putative Mg/Al/Sn - CO3, Mg/Al/Zr - CO3 and Co/Al/Sn - CO3 materials it has been unambiguously shown by X-ray absorption spectroscopy (XAS) and Mossbauer spectroscopy that the tetravalent cations are segregated from the LDH structure and form amorphous oxide-hke particles [69]. It was further demonstrated that the increased values of Uo previously attributed to the introduction of the large cations... 

Multlnuclear clusters of Fe(III) occur hound to the protein when Fe(II), at amounts less than or equal to that required to saturate the protein. Is allowed to oxidize JUi situ. The clusters, predicted from the results of EPR spectroscopy (35,38) and UV-difference spectroscopy (34), were observed and characterized by x-ray absorption (EXAFS) and MOssbauer spectroscopy (Figure 2 Ref. 39). Measurements were made with a complex of Fe(III) and the protein coats of apoferrltln after the binding of 10 Fe(II) atoms/molecule, the admission of air and equilibration for 24 hours. 

The other approach is to study real catalysts by using in-situ techniques such as infrared and Mossbauer spectroscopy, extended X-ray absorption fine structure (EXAFS) and XRD, either under reaction conditions, or - as occurs more often -under a controlled environment after quenching the reaction. These in-situ techniques, however, are usually not sufficiently specific to yield the desired atom-byatom characterization of the surface, and often they determine the overall properties of the particles. The situation is represented schematically in Figure 1.8. 

The third problem also concerns the choice of whether to leave out certain material. In a book of this size it is not possible to cover all branches of spectroscopy. Such decisions are difficult ones but I have chosen not to include spin resonance spectroscopy (NMR and ESR), nuclear quadrupole resonance spectroscopy (NQR), and Mossbauer spectroscopy. The exclusion of these areas, which have been well covered in other texts, has been caused, I suppose, by the inclusion, in Chapter 8, of photoelectron spectroscopy (ultraviolet and X-ray), Auger electron spectroscopy, and extended X-ray absorption fine structure, including applications to studies of solid surfaces, and, in Chapter 9, the theory and some examples of lasers and some of their uses in spectroscopy. Most of the material in these two chapters will not be found in comparable texts but is of very great importance in spectroscopy today. 

In MMO, compound Q has been identified as a coupled diiron(IV,IV) species, on the basis of its Mossbauer spectrum. While different structures for compound Q are possible, there is now some spectroscopic evidence (X-ray absorption fine structure and Mossbauer spectroscopy) that the diiron center in compound Q is a high-valent Fe2(/A-0)2 diamond core (Scheme 2). In the proposed mechanism, reaction... 

Mineralogical techniques such as X-ray diffraction, differential thermal analysis, Fourier transform infrared analysis, and Mossbauer spectroscopy may be useful for determining modes of occurrence of major elements in coal, but the ability of these techniques to determine the modes of occurrence of the minor- and trace-elements is quite limited. X-ray absorption-fine structure (XAFS) spectroscopy has been used to determine the modes of occurrence of several important minor and trace elements (e.g., arsenic and... 

The book opens with a short introduction into the nature of iron oxides. This is followed by a discussion of general preparative techniques (chapter 2). In chapter 3, techniques for characterization of the products - color measurement, electron microscopy. X-ray diffraction, infra red absorption spectroscopy, surface area measurement, thermoanalysis and Mossbauer spectroscopy - are briefly described with particular emphasis on their application to Fe oxides. 

Pinerii and coworkers, and a few other groups, have used ESR and Mossbauer spectroscopy as well as SANS, extended x-ray absorption fine structure (EX.AFS), and magnetization and susceptibility data to analyze local. struct.ure in perfluorinated ionomer membranes and the distribution of water within them isee, for inst,ance, (61-65) 1. The application of the KNDOR (electron nuclear double resonance) technique to deuteriated methanol-swollen Scunples of these membranes has been reportesd i-ecentiy (66). Photophysical methods have also tef n applied in hydration. si.udies of these membranes (67-69). Finally, some NMR results on the same hydrated perfluorinat,ed ionomer.s well as on hydrated... 

A number of physical techniques including Au Mossbauer, - NQR, - UV-visible absorption and MCD spectroscopies " and UV and X-ray photoelectron spectroscopies " have been used to probe the electronic structures of specific gold(III) complexes. 

Different characterization techniques are used to get an insight into the location of transition metal ions in an aluminophosphate framework. Generally, the data on the cation location are collected with difficulty since the metal concentration is low. In this regard, it is necessary to use more than one method if a reliable conclusion is to be reached (ie, the simultaneous application of several physical techniques is recommended). The following characterization methods are commonly applied diffuse reflectance UV-vis spectroscopy (DRS), electron spin resonance (ESR), electron spin echo modulation (ESEM), infrared (IR), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopies, as well as the nuclear magnetic resonance spectroscopy (NMR), Mossbauer spectroscopy and the X-ray absorption near-edge spectroscopy (XANES) and extended X-ray absorption spectroscopy for fine structure (EXAFS) (167,168) and references therein). 

V. Blanco-Gutierrez, F. Jimenez-Villacorta, P. Bonville, M.J. Torralvo-Fernandez, R. Saez-Puche, X-ray absorption spectroscopy and Mossbauer spectroscopy studies of super paramagnetic ZrrFe204 nanoparticles. J. Phys. Chem. C 115, 1627-1634 (2011)... 

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