Microwave Spin Resonance Absorption by Conduction Electrons in Metallic Sodium

1952 ◽  
Vol 88 (4) ◽  
pp. 951-952 ◽  
Author(s):  
T. W. Griswold ◽  
A. F. Kip ◽  
C. Kittel
Keyword(s):  
Resonance Absorption ◽  
Metallic Sodium ◽  
Conduction Electrons ◽  
Spin Resonance

Many-quantum transitions in conduction electron spin resonance

1968 ◽  
Vol 46 (15) ◽  
pp. 1685-1689
Author(s):  
T. A. Koss ◽  
S. Alexander ◽  
C. F. Schwerdtfeger
Keyword(s):  
Spin System ◽  
Bloch Equation ◽  
Effective Field ◽  
Resonance Absorption ◽  
Rotating Frame ◽  
Conduction Electrons ◽  
Spin Resonance ◽  
Quantum Transitions ◽  
Theory And Experiment ◽  
Modified Bloch Equation

Resonance absorption spectra have been observed which may be interpreted as many-quantum transitions where the quantization is along the effective field in the rotating frame. The spin system used was that of the conduction electrons in Li metal in a crystal of neutron irradiated LiF. An analysis of the experimental results using a modified Bloch equation under the assumptions that [Formula: see text] and that the spin system relaxes towards the instantaneous field is presented. The agreement between theory and experiment is excellent.

Light-induced reversible ionization of tetramethylphenylenediamine in an inorganic polymer of n-butyl orthotitanate

1988 ◽  
Vol 66 (8) ◽  
pp. 1931-1935
Author(s):  
Hisashi Ueda ◽  
Masahiro Kaise
Keyword(s):  
Relaxation Time ◽  
Electron Spin Resonance ◽  
Visible Light ◽  
Relative Intensity ◽  
Hyperfine Splitting ◽  
Resonance Absorption ◽  
Spin Quantum ◽  
Spin Quantum Number ◽  
Spin Resonance ◽  
Intensity Ratios

n-Butyl orthotitanate, BT, polymerized in tetrahydrofuran, if irradiated by visible light, gives a new electron spin resonance absorption that is not found before irradiation. In the present work, three different polymers of BT were synthesized by adding tetramethyl phenylenediamine (TMPD), dimethyl phenylenediamine (DMPD), or phenylenediamine (PD), to the solution of BT. The polymers thus prepared were tested to see if they give a new esr signal when irradiated by visible light. The polymer to which 1 mol% of TMPD was added gave TMPD•+ when irradiated by visible light, but the TMPD•+ signal decayed after the irradiation was discontinued. This change, therefore, is reversible. The resonant position of every hyperfine splitting line of the TMPD•+ found in this polymer coincided with that of TMPD•+ in solution, but the relative intensity ratios and the line width of each line depended on the nuclear spin quantum number of the coupling nuclei. This can be interpreted by the restricted rotational motion of TMPD•+ in the polymer matrix. The contribution of the non-diagonal term to the spin relaxation time would explain this phenomenon. In the case of the polymer to which DMPD was added, a small amount of DMPD•+ seemed to be formed, but no radical was detected in the case of the polymer to which PD was added.

Applications of ESR to Carbonaceous Materials

1982 ◽  
Vol 36 (1) ◽  
pp. 52-57 ◽  
Author(s):  
L. S. Singer ◽  
I. C. Lewis
Keyword(s):  
Free Radicals ◽  
Electron Spin Resonance ◽  
Low Temperature ◽  
Electron Spin ◽  
Paramagnetic Species ◽  
Carbonaceous Materials ◽  
Conduction Electrons ◽  
Spin Resonance ◽  
Higher Temperature ◽  
Low Temperature Pyrolysis

The applications of electron spin resonance (ESR) to carbonaceous materials are reviewed. The stable paramagnetic species observed in the products of low-temperature pyrolysis are odd-alternate neutral free radicals, whereas the unpaired spins of higher temperature carbons and graphites are primarily conduction electrons. The variety of ESR properties and phenomena requires special attention to techniques of measurement and interpretations of results. The relevance to the carbonization process of the free radicals observed by ESR is also discussed.

Mechanism of Hydrogen Embrittlement of Austenitic Steels

2007 ◽  
Vol 539-543 ◽  
pp. 4249-4254 ◽  
Author(s):  
V. Shivanyuk ◽  
Valentin G. Gavriljuk ◽  
Jacques Foct
Keyword(s):  
Hydrogen Embrittlement ◽  
Line Tension ◽  
Austenitic Steels ◽  
Hydrogen Atoms ◽  
Conduction Electrons ◽  
Metallic Character ◽  
Spin Resonance ◽  
Localization Of Plastic Deformation ◽  
Dislocation Sources ◽  
Strain Dependent

Three main hypotheses of hydrogen embrittlement (HE) of austenitic steels are discussed based on the studies of the interatomic interactions, hydrogen-induced phase transformations and dislocations properties. Measurements of electron spin resonance and ab initio calculations of the electron structure witness that the concentration of conduction electrons increases due to hydrogen, which enhances the metallic character of interatomic bonds. The hypothesis of brittle hydrogen-induced phases is disproved by the studies of the silicon-alloyed steels: the silicon-caused increase in the fraction of the εH martensite is accompanied by the decrease of HE. Studies of strain-dependent internal friction have shown the hydrogen-caused decrease in the start stress of microplasticity and increase in the velocity of dislocations in accordance with HELP hypothesis. A mechanism of HELP is proposed based on the hydrogencaused enhancement of the metallic character of interatomic bonds, which results in the local decrease of the shear modulus within the hydrogen atmospheres round the dislocations. As consequence, the line tension of the dislocations followed by the hydrogen atoms decreases, which finds its expression in the early start of dislocation sources, decreased distance between dislocations in the pile-ups and increased velocity of dislocations. A mechanism of localization of plastic deformation is proposed based on the observations of the hydrogen-enhanced concentration of equilibrium vacancies.

ESR Of Graphite-Like Amorphous Carbon Thin Film In The 20 – 340 K Temperature Range

2006 ◽  
Vol 984 ◽  
Author(s):  
Gustavo A. Viana ◽  
Francisco C. Marques
Keyword(s):  
Band Gap ◽  
Optical Band Gap ◽  
Ion Beam ◽  
Localized States ◽  
Paramagnetic Centers ◽  
Conduction Electrons ◽  
Temperature Range ◽  
Spin Resonance ◽  
Electron Energy Loss ◽  
Amorphous Carbon Thin Film

AbstractElectron spin resonance of graphite-like a-C thin films is investigated in the 20 K up to 340 K temperature range. The films with sp2 concentration of about 90 % (determined by electron energy loss spectroscopy), with no measurable optical band gap, were prepared by ion beam assisted sputtering. The results revealed an unexpected low density of paramagnetic centers, ascribed to itinerant states (conduction electrons) and not to localized states usually reported for a-C with band gap higher than 1.0 eV.

Electron Spin Resonance Absorption of Centres with an Orthorhombicg-Tensor in Polycrystalline Substances

1986 ◽  
Vol 94 (1) ◽  
pp. 267-274 ◽  
Author(s):  
F. Callens ◽  
R. Verbeeck ◽  
L. Martens ◽  
P. Matthys ◽  
E. Boesman
Keyword(s):  
Electron Spin Resonance ◽  
Electron Spin ◽  
Resonance Absorption ◽  
Spin Resonance
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