Mossbauer spectroscopy compound identification

Mossbauer spectroscopy is a selective tool for the quantitative analysis and spe-ciation of a very limited number of elements. It has been mainly used to study iron compounds—e.g., ceramics, as it gives valuable information about iron-bearing oxide and silicate minerals. This technique has been applied to the identification of the provenance of clay and used raw materials—the manufacturing method employed in pottery and, to a lesser extent, to the characterization of pigments and weathering crusts formed on stone monuments [23]. 

Mossbauer spectroscopy with the iodine isotopes is not a practical method for identification or quantification of organic compounds (nor of inorganics). It is most applicable for discerning electronic effects and charge states. For these applications, 129I gives far better results, and allows the separation of superposed subspectra. It is unfortunate that its use requires radiochemical techniques and very small scales. 

The influence of the zeolite environment on the XPS BE of dispersed ions (vide supra) means that reference compoimds for this type of investigation are not easily available. This is not so much a problem for the starting material for which the highest oxidation state of the element is often plausible, but the identification of intermediate states, and sometimes of the final state of reduction, is not straightforward. As a first approximation, BE shifts known from bulk components (e.g., coordination compounds) are often used in the analysis of zeolite systems. Combination with bulk techniques sensitive to electronic structure can provide additional information notwithstanding possible differences between the conditions in the bulk crystallite and the surface layer. Thus, IR of adsorbed CO has been used to differentiate between Pt andPt(O) atoms in H-ZSM-5 [131], EXAFS was able to detect very small intra-zeolite Cu(0) clusters formed from Cu+ with almost identical XPS/XAES signature [108], Mossbauer spectroscopy suggested the presence of Fe in zeolites with doubtftil Fe 2p satellites [116], and ESR was employed to support the occurrence of Pd+ in the reduction of intra-zeolite Pd(II) [126,127]. 

Single-crystal X-ray crystallography remains the only definitive technique for the structural characterization of heteronuclear gold cluster compounds, although other techniques, in particular Mossbauer, NMR, IR, and fast atom bombardment mass spectroscopies (FABMS), have yielded valuable information, especially concerning the nature of these species in solution. Electron spectroscopy, which has proved to be of great value in the identification of homonuclear gold cluster compounds (210) has received little attention by workers in this area,... 

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