Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Figures Only Full Text Full Text (PDF) Supplementary Data Info Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Ohta, A. Articles by Kawabe, I. Search for Related Content GeoRef GeoRef Citation

Influence of multi-electron excitation on EXAFS spectroscopy of trivalent rare-earth ions and elucidation of change in hydration number through the series

¹ Geological Survey of Japan, AIST, Tsukuba 305-8567, Japan
² Geochemical Laboratory, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan
³ Faculty of Education and Human Sciences, Yokohama National University, Kanagawa, 240-8501, Japan
⁴ Photon Factory, Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan
⁵ Department of Earth and Planetary Sciences, Graduate School of Environmental Studies, Nagoya University, Nagoya 464-8602, Japan

Correspondence: ^* E-mail: a.ohta{at}aist.go.jp

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 x 10^–3 Ų for La³⁺ to 7.9, 2.31 Å, and 5.7 x 10^–3 Ų 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.

Key Words: EXAFS • rare-earth elements • multi-electron excitation • hydration structure • structural change

This article has been cited by other articles:

				A. Ohta, H. Kagi, M. Nomura, H. Tsuno, and I. Kawabe Coordination study of rare earth elements on Fe oxyhydroxide and Mn dioxides: Part I. Influence of a multi-electron excitation on EXAFS analyses of La, Pr, Nd, and Sm American Mineralogist, April 1, 2009; 94(4): 467 - 475. [Abstract] [Full Text] [PDF]

				A. Ohta, H. Kagi, M. Nomura, H. Tsuno, and I. Kawabe Coordination study of rare earth elements on Fe oxyhydroxide and Mn dioxides: Part II. Correspondence of structural change to irregular variations of partitioning coefficients and tetrad effect variations appearing in interatomic distances American Mineralogist, April 1, 2009; 94(4): 476 - 486. [Abstract] [Full Text] [PDF]