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Coordination chemistry of iron in glasses contributing to remote-sensed spectra of the moonFerric iron and tetrahedrally coordinated Fe(2+) ions are identified using Moessbauer and electronic absorption spectroscopic measurements of synthetic glasses equilibrated at P(O2) less than 10 to the -11 atm, simulating the Luna 24 brown glass and Apollo 15 green glass compositions. The presence of 10-20% ferric iron in these low Ti glasses is a result of the absence of Ti(3+) ions. In the brown glass absorption spectra, tetrahedral Fe(3+) and Fe(2+) ions induce an extension of the oxygen-metal charge transfer band into the visible region further than in the green glass containing predominantly octahedral Fe(2+) and Fe(3+) ions. Whereas the glass one-micron band originates from crystal field transitions in octahedral Fe(2+), the glass two-micron band is now positively correlated with tetrahedral Fe(2+) rather than with Fe(2+) ions in pyroxene M2-like sites in the glass structure. The tetrahedral Fe(2+) do not, however, substitute for Si(4+) in glass network-forming sites, instead occurring as network modifiers in larger tetrahedral interstices. The effect of temperature is to induce a pronounced red-shift of the oxygen-iron charge transfer absorption edge, especially for the brown glass, and to intensify significantly the tetrahedral Fe(2+) crystal field two micron band.
Document ID
19820048184
Acquisition Source
Legacy CDMS
Document Type
Conference Proceedings
Authors
Dyar, M. D.
(Massachusetts Inst. of Tech. Cambridge, MA, United States)
Burns, R. G.
(MIT Cambridge, MA, United States)
Date Acquired
August 10, 2013
Publication Date
January 1, 1982
Subject Category
Lunar And Planetary Exploration
Meeting Information
Meeting: Lunar and Planetary Science Conference
Location: Houston, TX
Start Date: March 16, 1981
End Date: March 20, 1981
Accession Number
82A31719
Funding Number(s)
CONTRACT_GRANT: NSG-7604
Distribution Limits
Public
Copyright
Other

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