Temperature dependence of the exchange interaction and applications to electron paramagnetic resonance

AbstractThree different Electron Paramagnetic Resonance (EPR) signals, one trigonal and two orthorhombic, which originates from iron-indium pairs in silicon are investigated. It is shown that the two orthorhombic spectra can be explained as transitions within the two doublets of a S=3/2 system with a large zero-field splitting. The temperature dependence of-the intensities reveals that the newly discovered spectrum corresponds to the lower doublet and that the zero-field splitting is 9.8 ± 2.0 cm-1.

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An Electrolytically Generated, Localized Hole Center in Quartz

Zeitschrift für Naturforschung A ◽

10.1515/zna-1989-0405 ◽

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.

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

Canadian Journal of Chemistry ◽

10.1139/v65-459 ◽

1965 ◽

Vol 43 (12) ◽

pp. 3294-3303 ◽

Cited By ~ 7

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.

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