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Single-crystal EPR and ENDOR study of an Al-O (super -) center in prehnite; implications for aluminum-associated oxyradicals in layer silicates

Mao Mao, Mark J. Nilges and Yuanming Pan
Single-crystal EPR and ENDOR study of an Al-O (super -) center in prehnite; implications for aluminum-associated oxyradicals in layer silicates
European Journal of Mineralogy (June 2010) 22 (3): 381-392

Abstract

Single-crystal electron paramagnetic resonance (EPR) spectra of gamma-ray-irradiated prehnite (Jeffrey mine, Quebec, Canada) measured at 298 and 160 K reveal an aluminum-associated oxygen hole center (Al-O (super -) ). Spin Hamiltonian parameters g and A( (super 27) Al) fitted from the 298 K spectra suggest that this Al-O (super -) center represents hole trapping on an apical hydroxyl oxygen atom (after removal of the proton) coordinated to an octahedral Al (super 3+) ion (i.e., an [ (super .) OAlO (sub 4) (OH)] center from the [(OH)AlO (sub 4) (OH)] precursor, where . denotes the unpaired spin). Pulsed electron nuclear double resonance (ENDOR) spectra measured at 25 K allow the identification and quantitative analysis of two sets of (super 27) Al hyperfine structures and five proton hyperfine structures, which are all consistent with the proposed structural model. Isothermal and isochronal annealing experiments show that this center is bleached out completely at 375 degrees C, but can be readily restored by gamma-ray irradiation, and exhibits second-order decay kinetics. These results from the Al-O (super -) center in prehnite provide support for and new insights into Clozel et al.'s (1995) (super VI) Al-O (super -) - (super VI) Al model for B-centers in kaolinite.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 22
Serial Issue: 3
Title: Single-crystal EPR and ENDOR study of an Al-O (super -) center in prehnite; implications for aluminum-associated oxyradicals in layer silicates
Affiliation: University of Saskatchewan, Department of Geological Sciences, Saskatoon, SK, Canada
Pages: 381-392
Published: 201006
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 43
Accession Number: 2010-060658
Categories: Mineralogy of silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: University of Illinois at Urbana-Champaign, USA, United States
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: 201033
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