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Optical absorption spectroscopy study of three synthetic V (super 3+) -bearing clinopyroxenes

Michail N. Taran and Haruo Ohashi
Optical absorption spectroscopy study of three synthetic V (super 3+) -bearing clinopyroxenes (in The 7th European conference on Mineralogy and spectroscopy, Monika Koch-mueller (editor), Michael Fechtelkord (editor), Vladimir Khomenko (editor) and Sergio Speziale (editor))
European Journal of Mineralogy (September 2012) 24 (5): 823-829

Abstract

Optical absorption spectra of synthetic clinopyroxenes of NaVSi (sub 2) O (sub 6) , LiVSi (sub 2) O (sub 6) and CaVAlSiO (sub 6) composition consist of a high-energy absorption edge and two broad absorption bands nu (sub 1) and nu (sub 2) at around 15,000 cm (super -1) and 22,000 cm (super -1) caused by spin-allowed electronic transitions (super 3) T (sub 1) (sub g) ( (super 3) F) --> (super 3) T (sub 2) (sub g) ( (super 3) F) and (super 3) T (sub 1) (sub g) ( (super 3) F) --> (super 3) T (sub 1) (sub g) ( (super 3) P) of V (super 3+) in octahedral M1-site of the clinopyroxene structure. In polarized spectra of NaVSi (sub 2) O (sub 6) and LiVSi (sub 2) O (sub 6) pyroxenes the relative intensities of the polarized components of nu (sub 1) - and nu (sub 2) -bands are rather different, revealing differences in the distortion of VO (sub 6) -octahedra in the two structures. In spite of a formal similarity to the absorption spectra of Cr (super 3+) in Cr-bearing clinopyroxenes, the pressure-induced behaviour of the spin-allowed bands of V (super 3+) in NaVSi (sub 2) O (sub 6) -pyroxene is noticeably different: although they also shift to higher energies as do the bands of Cr (super 3+) , the integral intensity of the nu (sub 1) -band remains nearly constant within uncertainty whereas that of the nu (sub 2) -band somewhat decreases, in contrast to Cr (super 3+) for which the spin-allowed bands significantly decrease. Comparing with k (sub oct) (super loc) -value of CrO (sub 6) -octahedron in NaCrSi (sub 2) O (sub 6) kosmochlor, approximately 196 GPa, the VO (sub 6) -octahedron in NaVSi (sub 2) O (sub 6) clinopyroxene structure is considerably softer, with k (sub oct) (super loc) nearly equal 163 GPa. The <V - O>distances derived from the optical absorption spectra can fairly well be approximated by a linear dependence. The Racah parameter B of V (super 3+) evidently decreases with increasing pressure from approximately 554 cm (super -1) at 10 (super -4) GPa to 508 cm (super -1) at 10.7 GPa, thus indicating that V - O bonds in the VO (sub 6) -octahedra become more covalent.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 24
Serial Issue: 5
Title: Optical absorption spectroscopy study of three synthetic V (super 3+) -bearing clinopyroxenes
Title: The 7th European conference on Mineralogy and spectroscopy
Author(s): Taran, Michail N.Ohashi, Haruo
Author(s): Koch-mueller, Monikaeditor
Author(s): Fechtelkord, Michaeleditor
Author(s): Khomenko, Vladimireditor
Author(s): Speziale, Sergioeditor
Affiliation: National Academy of Science of Ukraine, Institute of Geochemistry, Mineralogy and Ore Formation, Kiev, Ukraine
Affiliation: Deutsches GeoForschungsZentrum, Helmholtz-Zentrum Potsdam, Potsdam, Germany
Pages: 823-829
Published: 201209
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Germany
Meeting name: The 7th European conference on Mineralogy and spectroscopy
Meeting location: Potsdam, DEU, Germany
Meeting date: 20110904Sept. 4-7, 2011
References: 21
Accession Number: 2012-086345
Categories: Mineralogy of silicates
Document Type: Serial Conference document
Bibliographic Level: Analytic
Illustration Description: illus. incl. 4 tables
Secondary Affiliation: Ruhr-Universitaet Bochum, DEU, GermanyHASHI Institute for Silicate Science, JPN, Japan
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Schweizerbart'sche Verlagsbuchhandlung. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201245
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