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Biradical states of oxygen-vacancy defects in α-quartz: centers and
Several new radiation defects with total electron spin S = 1 occurring in electron-irradiated, synthetic α-quartz have been observed by using electron paramagnetic resonance spectroscopy. These defects are considered to be biradicals, i.e., pairs of S = 1/2 species. The concentration of these cent...
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Published in: | Physics and chemistry of minerals 2011-09, Vol.38 (8), p.647-654 |
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Main Authors: | , |
Format: | Article |
Language: | English |
Subjects: | |
Online Access: | Get full text |
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Summary: | Several new radiation defects with total electron spin
S
= 1 occurring in electron-irradiated, synthetic α-quartz have been observed by using electron paramagnetic resonance spectroscopy. These defects are considered to be biradicals, i.e., pairs of
S
= 1/2 species. The concentration of these centers depends on the condition of the fast-electron irradiation. They have different decay behaviors that allow measurements of any individual species especially when it predominates over the others. The primary spin Hamiltonian parameter matrices
g
1
,
g
2
,
D
have now been determined for two similar defects, which herein are labeled
and
. Inter-electron distances estimated by using the magnetic dipole model, suggest that the structures of centers
and
both involve the unpaired electrons each located in orbitals of two silicon atoms next to a common oxygen vacancy but which have slightly different Si–Si distances at 0.90 and 0.79 nm, respectively. This model is consistent with previous DFT calculations of the triplet configurations with local energetic minima. Observed decay behaviors suggest a transformation of centers
to the analogous
center. These triplet centers in quartz provide new insights into the structures of analogous defects in amorphous silica. |
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ISSN: | 0342-1791 1432-2021 |
DOI: | 10.1007/s00269-011-0437-0 |