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https://hdl.handle.net/2440/66165
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Type: | Journal article |
Title: | Molybdenum X-ray absorption edges from 200 to 20,000 eV: The benefits of soft X-ray spectroscopy for chemical speciation |
Author: | George, S. Drury, O. Fu, J. Friedrich, S. Doonan, C. George, G. White, J. Young, C. Cramer, S. |
Citation: | Journal of Inorganic Biochemistry, 2009; 103(2):157-167 |
Publisher: | Elsevier Science Inc |
Issue Date: | 2009 |
ISSN: | 0162-0134 1873-3344 |
Statement of Responsibility: | Simon J. George, Owen B. Drury, Juxia Fu, Stephan Friedrich, Christian J. Doonan, Graham N. George, Jonathan M. White, Charles G. Young, Stephen P. Cramer |
Abstract: | We have surveyed the chemical utility of the near-edge structure of molybdenum X-ray absorption edges from the hard X-ray K-edge at 20,000eV down to the soft X-ray M(4,5)-edges at approximately 230eV. We compared, for each edge, the spectra of two tetrahedral anions, MoO(4)(2-) and MoS(4)(2-). We used three criteria for assessing near-edge structure of each edge: (i) the ratio of the observed chemical shift between MoO(4)(2-) and MoS(4)(2-) and the linewidth, (ii) the chemical information from analysis of the near-edge structure and (iii) the ease of measurement using fluorescence detection. Not surprisingly, the K-edge was by far the easiest to measure, but it contained the least information. The L(2,3)-edges, although harder to measure, had benefits with regard to selection rules and chemical speciation in that they had both a greater chemical shift as well as detailed lineshapes which could be theoretically analyzed in terms of Mo ligand field, symmetry, and covalency. The soft X-ray M(2,3)-edges were perhaps the least useful, in that they were difficult to measure using fluorescence detection and had very similar information content to the corresponding L(2,3)-edges. Interestingly, the soft X-ray, low energy ( approximately 230eV) M(4,5)-edges had greatest potential chemical sensitivity and using our high-resolution superconducting tunnel junction (STJ) fluorescence detector they appear to be straightforward to measure. The spectra were amenable to analysis using both the TT-multiplet approach and FEFF. The results using FEFF indicate that the sharp near-edge peaks arise from 3d-->5p transitions, while the broad edge structure has predominately 3d-->4f character. A proper understanding of the dependence of these soft X-ray spectra on ligand field and site geometry is necessary before a complete assessment of the utility of the Mo M(4,5)-edges can be made. This work includes crystallographic characterization of sodium tetrathiomolybdate. |
Keywords: | Molybdenum XANES Near-edge spectra XAS X-ray absorption spectroscopy Soft X-ray spectroscopy L-edge spectroscopy M-edge spectroscopy Superconducting tunnel junctions STJ X-ray detectors Molybdate Thiomolybdate Sodium tetrathiomolybdate Crystal structure |
Rights: | © 2008 Elsevier Inc. All rights reserved. |
DOI: | 10.1016/j.jinorgbio.2008.09.008 |
Grant ID: | ARC |
Published version: | http://dx.doi.org/10.1016/j.jinorgbio.2008.09.008 |
Appears in Collections: | Aurora harvest 5 Chemistry publications Environment Institute publications |
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