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Influence of multi-electron excitation on EXAFS spectroscopy of trivalent rare-earth ions and elucidation of change in hydration number through the series.
- Source :
-
American Mineralogist . Aug2008, Vol. 93 Issue 8/9, p1384-1392. 9p. - Publication Year :
- 2008
-
Abstract
- We have made a detailed study of the extended X-ray absorption fine spectra (EXAFS) at the K edge of aqueous Y ion and at L3 edges of aqueous lanthanide ions and thereby elucidated the systematic changes in their hydration structures. Anomalous peaks arising from double-electron excitation (2p, 4d → 5d, 5d) appear in the EXAFS signals of La3+-Tb3+ between 5-7 Å-1. We established a removal process of double-electron excitation from EXAFS spectra. Using that process, we confirmed that the intensity and energy position of the extracted double-electron excitation are comparable to previously reported data. The presence of double-electron excitation engenders a smaller error than the errors estimated in the fitting process. Consequently, double-electron excitation does not seriously affect the determination of the structures of REE3+ aquo ions in the first coordination sphere. Subsequent EXAFS analyses of hydrated REE3+ ions suggest that the hydration numbers, the interatomic distances, and the Debye-Waller factors decrease from 9.7, 2.55 Å, and 9.0 × 10-3 Å2 for La3+ to 7.9, 2.31 Å, and 5.7 × 10-3 Å2 for Lu3+. These parameters change as a sigmoid curve with increasing atomic number. The hydration structures of REE3+ ions are inferred to change from the nonahydrated structure for La3+-Nd3+ to the octahydrated structure for Tb3+-Lu3+ through intermediate structures for Sm3+, Eu3+, and Gd3+. In addition, the hydration state of Y3+ closely resembles that of Ho3+ because the two have almost identical ionic radii. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 0003004X
- Volume :
- 93
- Issue :
- 8/9
- Database :
- Academic Search Index
- Journal :
- American Mineralogist
- Publication Type :
- Academic Journal
- Accession number :
- 34128900
- Full Text :
- https://doi.org/10.2138/am.2008.2628