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Electronic transitions of iron in almandine-composition glass to 91 GPa

Author(s): Dorfman, Susannah M; Dutton, Sian E; Potapkin, Vasily; Chumakov, Aleksandr I; Rueff, Jean-Pascal; et al

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Abstract: Valence and spin states of Fe were investigated in a glass of almandine (Fe3Al2Si3O12) composition to 91 GPa by X-ray emission spectroscopy and energy- and time-domain synchrotron Mössbauer spectroscopy in the diamond-anvil cell. Changes in optical properties, total spin moment and Mössbauer parameters all occur predominantly between 1 bar and ~30 GPa. Over this pressure range, the glass changes from translucent brown to opaque and black. The total spin moment of the glass derived from X-ray emission spectroscopy decreases by ~20%. The complementary Mössbauer spectroscopy approaches reveal consistent changes in sites corresponding to 80–90% Fe2+ and 10–20% Fe3+. The high-spin Fe2+ doublet exhibits a continuous decrease in isomer shift and increase in line width and asymmetry. A high-spin Fe3+ doublet with quadrupole splitting of ~1.2 mm/s is replaced by a doublet with quadrupole splitting of ~1.9 mm/s, a value higher than all previous measurements of high-spin Fe3+ and consistent with low-spin Fe3+. These observations suggest that Fe3+ in the glass undergoes a continual transition from a high-spin to a low-spin state between 1 bar and ~30 GPa. Almandine glass is not expected to undergo any abrupt transitions in electronic state at deep mantle pressures.
Publication Date: 2016
Citation: Dorfman, Susannah M., Sian E. Dutton, Vasily Potapkin, Aleksandr I. Chumakov, Jean-Pascal Rueff, Paul Chow, Yuming Xiao et al. "Electronic transitions of iron in almandine-composition glass to 91 GPa." American Mineralogist 101, no. 7 (2016): 1659-1667. doi:10.2138/am-2016-5606.
DOI: doi:10.2138/am-2016-5606
ISSN: 0003-004X
Pages: 1659 - 1667
Language: English
Type of Material: Journal Article
Journal/Proceeding Title: American Mineralogist
Version: Author's manuscript

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