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Nuclear resonant X-ray spectroscopy of (Mg,Fe)SiO_3 orthoenstatites

Jackson, Jennifer M. and Hamecher, Emily A. and Sturhahn, Wolfgang (2009) Nuclear resonant X-ray spectroscopy of (Mg,Fe)SiO_3 orthoenstatites. European Journal of Mineralogy, 21 (3). pp. 551-560. ISSN 0935-1221. doi:10.1127/0935-1221/2009/0021-1932.

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We present nuclear resonant inelastic X-ray scattering (NRIXS) and synchrotron Mössbauer spectroscopy (SMS) measurements, both nuclear resonant X-ray spectroscopic methods, on synthetic samples of orthoenstatite-structured (Mg,^(57)Fe)SiO_3, a representative component in Earth's upper mantle. All measurements were performed at ambient conditions. NRIXS spectra were measured for three samples of orthoenstatite containing 20, 13, and 7 mol% FeSiO_3. The Debye sound velocities were determined from the low-energy region of the partial phonon density of states (PDOS). With known density and bulk modulus, the shear modulus, compressional and shear wave velocities have been computed. The sound velocities obtained from NRIXS are in good agreement with sound velocities obtained using Brillouin spectroscopy and ultrasonic methods for similar compositions. An important advantage of NRIXS is access to additional thermodynamic information, such as the average force constant, mean-square displacement, obtained from the PDOS. We discuss the contribution of the vibrational spectra to these quantities. In addition to the PDOS, the electronic environment of the iron sites in (Mg_(0.87)^(57)Fe_(0.13))SiO_3 orthoenstatite was determined using ^(57)Fe SMS and conventional Mössbauer spectroscopy. Evaluation of the Mössbauer spectra reveals two distinct iron sites, which are well distinguished by their hyperfine fields. The minority and majority sites are consistent with high-spin Fe^(2+) in the M1 and M2 sites, respectively.

Item Type:Article
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Jackson, Jennifer M.0000-0002-8256-6336
Sturhahn, Wolfgang0000-0002-9606-4740
Additional Information:© 2009 E. Schweizerbart’sche Verlagsbuchhandlung. Received 27 November 2008. Modified version received 16 January 200. 9 Accepted 11 March 2009. We thank Y. Fei (Carnegie Institution of Washington) for synthesizing the orthoenstatite samples, E.E. Alp (ANL) for performing the conventional Mo¨ssbauer measurements, J. Zhao (ANL) for technical assistance at sector 3, D. Zhang (Caltech) for discussions, and two anonymous reviewers for their comments and suggestions. Support for this work was provided by the National Science Foundation (NSF) EAR #0711542 (JMJ). Use of the Advanced Photon Source was supported by the US DOE, Office of Science, and BES (DE-AC02-06CH11357). This research was partially supported by COMPRES under NSF Cooperative Agreement EAR 06–49658.
Group:Seismological Laboratory, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
NSFEAR 0711542
US Department of EnergyUNSPECIFIED
Office of ScienceUNSPECIFIED
British Ecological SocietyDE-AC02-06CH11357
NSFEAR 06–49658
Issue or Number:3
Record Number:CaltechAUTHORS:20090903-134645269
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15581
Deposited By: Ruth Sustaita
Deposited On:22 Sep 2009 17:08
Last Modified:08 Nov 2021 23:20

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