Molybdenum X-ray absorption edges from 200 to 20,000 eV: The benefits of soft X-ray spectroscopy for chemical speciation

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dc.contributor.authorGeorge, S.
dc.contributor.authorDrury, O.
dc.contributor.authorFu, J.
dc.contributor.authorFriedrich, S.
dc.contributor.authorDoonan, C.
dc.contributor.authorGeorge, G.
dc.contributor.authorWhite, J.
dc.contributor.authorYoung, C.
dc.contributor.authorCramer, S.
dc.date.issued2009
dc.description.abstractWe 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.
dc.description.statementofresponsibilitySimon J. George, Owen B. Drury, Juxia Fu, Stephan Friedrich, Christian J. Doonan, Graham N. George, Jonathan M. White, Charles G. Young, Stephen P. Cramer
dc.identifier.citationJournal of Inorganic Biochemistry, 2009; 103(2):157-167
dc.identifier.doi10.1016/j.jinorgbio.2008.09.008
dc.identifier.issn0162-0134
dc.identifier.issn1873-3344
dc.identifier.urihttp://hdl.handle.net/2440/66165
dc.language.isoen
dc.publisherElsevier Science Inc
dc.relation.grantARC
dc.rights© 2008 Elsevier Inc. All rights reserved.
dc.source.urihttps://doi.org/10.1016/j.jinorgbio.2008.09.008
dc.subjectMolybdenum
dc.subjectXANES
dc.subjectNear-edge spectra
dc.subjectXAS
dc.subjectX-ray absorption spectroscopy
dc.subjectSoft X-ray spectroscopy
dc.subjectL-edge spectroscopy
dc.subjectM-edge spectroscopy
dc.subjectSuperconducting tunnel junctions
dc.subjectSTJ X-ray detectors
dc.subjectMolybdate
dc.subjectThiomolybdate
dc.subjectSodium tetrathiomolybdate
dc.subjectCrystal structure
dc.titleMolybdenum X-ray absorption edges from 200 to 20,000 eV: The benefits of soft X-ray spectroscopy for chemical speciation
dc.typeJournal article
pubs.publication-statusPublished

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