An Electrolytically Generated, Localized Hole Center in Quartz

1989 ◽  
Vol 44 (4) ◽  
pp. 278-282
Author(s):  
A. B. Vassilikou-Dova ◽  
K. Eftaxias ◽  
G. Lehmann
Keyword(s):  
Activation Energy ◽  
Electron Paramagnetic Resonance ◽  
Temperature Dependence ◽  
Free Electron ◽  
Room Temperature ◽  
Hole Center ◽  
Paramagnetic Resonance ◽  
Tentative Model ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

Abstract In natural smoky quartz and neutron-irradiated, initially colorless quartz a new hole center was formed electrolytically at temperatures near 1100 K in addition to the well-known smoky quartz center. Unlike the latter its electron paramagnetic resonance spectra can already be measured at room temperature due to firm localization of the hole on one oxygen. It is characterized by fairly small hyperfine splittings due to Al impurity and significant deviations of all three principal g factors from that of a free electron. A tentative model for the structure of this center is proposed.An activation energy of 215 kJ/mol was determined for this electrolytic coloration from the temperature dependence of the electrolysis currents.

ALICYCLIC KETYLS: II. TEMPERATURE DEPENDENCE OF THE CONFORMATIONAL MOBILITY OF MEDIUM-SIZED RINGS

1965 ◽  
Vol 43 (12) ◽  
pp. 3294-3303 ◽  
Author(s):  
J. W. Lown
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Close Agreement ◽  
Conformational Equilibrium ◽  
Dihedral Angles ◽  
Paramagnetic Resonance ◽  
Conformational Equilibria ◽  
Electron Paramagnetic ◽  
Hyperfine Couplings

The electron paramagnetic resonance spectra of ketyls derived from alicyclic ketones containing from 6 to 12 carbons have been recorded in 1,2-dimethoxyethane or dimethoxymethane at temperatures from −96 to +87 °C. At −96° individual conformers of the cyclohexyl ketyl are observed with hyperfine couplings in close agreement with that of the conformationally 'frozen' 4-tert-butyl analogue at room temperature. The cycloheptyl ketyl conformational equilibrium between forms which have a plane of symmetry through the C—O bond axis is 'frozen' with respect to the spectrometer frequency at temperatures from −40 to +88 °C. Cyclooctyl ketyl equilibrates at ordinary temperatures between two conformers lacking a plane of symmetry through the C—O bond axis. The electron paramagnetic resonance spectra of the ketyls derived from 10- and 12-membered rings show dramatic temperature dependence, which is interpreted in terms of two or more simultaneous conformational equilibria. Values for the dihedral angles of the alpha protons and for the spin density on the sp2 carbon are derived.

ALICYCLIC KETYLS: I. ANGULAR DEPENDENCE OF HYPERFINE COUPLING AND CONFORMATIONAL MOBILITY OF CYCLOHEXANONE KETYLS

1965 ◽  
Vol 43 (9) ◽  
pp. 2571-2575 ◽  
Author(s):  
J. W. Lown
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Angular Dependence ◽  
Room Temperature ◽  
Hyperfine Coupling ◽  
Conformational Mobility ◽  
Paramagnetic Resonance ◽  
Methyl Group ◽  
Tert Butyl ◽  
Hyperfine Splittings ◽  
Electron Paramagnetic

The electron paramagnetic resonance (e.p.r.) spectra of ketyls derived from cyclopentanone and 4-tert-butyl, 4-methyl, 3-methyl, and unsubstituted cyclohexanone have been recorded in dimethoxymethane at room temperature. The proton hyperfine splittings (aH) observed with rigid ketyls are consistent with a dihedral angular (θ) dependence of hyperfine coupling of the form, aH = 4.8 + 9.6 cos2 θ. Conformational averaging of the hyperfine coupling is observed with 4-methyl, 3-methyl, and unsubstituted cyclohexanone ketyls. The conformer populations calculated from the e.p.r. spectra are in accordance with A values for the methyl group derived from non-radical cyclohexane compounds.

Electron Paramagnetic Resonance in Cu2O Compared with Other Semiconducting Properties

1971 ◽  
Vol 49 (10) ◽  
pp. 1275-1283 ◽  
Author(s):  
J. C. W. Taylor ◽  
F. L. Weichman ◽  
R. E. D. McClung
Keyword(s):  
Activation Energy ◽  
Electron Paramagnetic Resonance ◽  
Single Crystals ◽  
Room Temperature ◽  
Starting Material ◽  
Paramagnetic Resonance ◽  
Semiconducting Properties ◽  
Wide Range ◽  
Temperature Activation ◽  
Electron Paramagnetic

Electron paramagnetic resonance spectra have been observed in single crystals of Cu2O at 4.2 °K. Six samples cut from the same starting material were individually heated under a wide range of vacuum conditions and comparison was made between the observed e.p.r. spectrum and the luminescence, activation energy, and photoconductivity in the same sample. No direct relationships between e.p.r. spectra and the luminescence and photoconductivity were found although a good correlation between the complexity of the e.p.r. spectra and the room temperature activation energy was observed.

Temperature Dependent Line-Shape of the Silicon Dangling Bond EPR-Resonance in Polycrystalline Silicon

1996 ◽  
Vol 452 ◽  
Author(s):  
N. H. Nickel ◽  
E. A. Schiff
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Polycrystalline Silicon ◽  
Room Temperature ◽  
Dangling Bond ◽  
Temperature Dependent ◽  
Paramagnetic Resonance ◽  
Temperature Electron ◽  
Motional Narrowing ◽  
G Value ◽  
Electron Paramagnetic

AbstractThe temperature dependence of the silicon dangling-bond resonance in polycrystalline (poly-Si) and amorphous silicon (a-Si:H) was measured. At room temperature, electron paramagnetic resonance (EPR) measurements reveal an isotropie g-value of 2.0055 and a line width of 6.5 and 6.1 G for Si dangling-bonds in a-Si:H and poly-Si, respectively. In both materials spin density and g-value are independent of temperature. While in a-Si:H the width of the resonance did not change with temperature, poly-Si exhibits a remarkable T dependence of ΔHpp. In unpassivated poly-Si a pronounced decrease of ΔHpp is observed for temperatures above 300 K. At 384 K ΔHpp reaches a minimum of 5.1 G, then increases to 6.1 G at 460 K, and eventually decreases to 4.6 G at 530 K. In hydrogenated poly-Si ΔHpp decreases monotonically above 425 K. The decrease of ΔHpp is attributed to electron hopping causing motional narrowing. An average hopping distance of 15 and 17.5 Å was estimated for unhydrogenated and H passivated poly-Si, respectively.

Room Temperature Electron Paramagnetic Resonance (EPR) Signal Storage

1969 ◽  
Author(s):  
D.A. Bozanic ◽  
D.C. Buck ◽  
F.H. Harris ◽  
R.E. Huber ◽  
D. Mergerian ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Room Temperature ◽  
Paramagnetic Resonance ◽  
Temperature Electron ◽  
Epr Signal ◽  
Electron Paramagnetic

Paramagnetic Defects in Benitoite

1991 ◽  
Vol 46 (7) ◽  
pp. 579-582 ◽  
Author(s):  
A. B. Vassilikou-Dova ◽  
K. Eftaxias
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Hyperfine Interaction ◽  
Relative Intensity ◽  
Room Temperature ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic ◽  
Magnetic Defects

Abstract In clear, blue, transparent bipyramidal crystals of the rare mineral benitoite, BaTiSi3O9, para­ magnetic defects have been investigated by electron paramagnetic resonance at room temperature and 9.43 GHz. They are attributed to Sn3+ and Fe3+ . A pair of satellites recorded for a wide angular rage around B0 || c (~40°) and a relative intensity of ~ 13% to the central signal is most likely due to hyperfine interaction with 117Sn and 119Sn isotopes. Attempts to bleach the colour of the crystal were unsuccessful.

Transient electron paramagnetic resonance of the triplet state of P700 in photosystem I: Evidence for triplet delocalization at room temperature

Biochemistry ◽  
1993 ◽  
Vol 32 (18) ◽  
pp. 4842-4847 ◽  
Author(s):  
Ina Sieckmann ◽  
Klaus Brettel ◽  
Christian Bock ◽  
Arthur van der Est ◽  
Dietmar Stehlik
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Triplet State ◽  
Photosystem I ◽  
Room Temperature ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic
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