Electron paramagnetic resonance spectra of some sulfur-containing radicals

1970 ◽  
Vol 48 (24) ◽  
pp. 3872-3876 ◽  
Author(s):  
P. S. H. Bolman ◽  
I. Safarik ◽  
D. A. Stiles ◽  
W. J. R. Tyerman ◽  
O. P. Strausz
Keyword(s):  
Thiyl Radical ◽  
Radical Product ◽  
Paramagnetic Resonance ◽  
Vycor Glass ◽  
Porous Vycor Glass ◽  
Temperature Matrix ◽  
G Value ◽  
Electron Paramagnetic ◽  
Sulfur Containing ◽  
Free Radical Product

The e.p.r. spectra from the low temperature matrix photolysis of several mercaptans, disulfides, and cyclic sulfides have been recorded and compared to those obtained in the photolysis of these materials adsorbed on a porous Vycor glass. The spectra of the adsorbed radicals are characterized by an enhanced thermal stability and a shift of the highest sulfur g-value to higher fields. The only free radical product in the photolysis of mercaptans and disulfides is the thiyl radical. The cyclic sulfides [Formula: see text] appear to yield•CH2—(CH2)n—S•type diradicals, while the cyclic disulfide [Formula: see text][Formula: see text] gives the [Formula: see text] diradical.

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.

Evaluation of EPR monitoring of singlet oxygen production using the photosensitizer chloroboron subphthalocyanine

2011 ◽  
Vol 15 (02) ◽  
pp. 118-121 ◽  
Author(s):  
Lawrence J. Berliner ◽  
Helmut Görner ◽  
Heinz-Peter Schuchmann
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Singlet Oxygen ◽  
Reaction System ◽  
Oxygen Production ◽  
Crucial Aspect ◽  
Singlet Molecular Oxygen ◽  
Radical Product ◽  
Paramagnetic Resonance ◽  
Boron Subphthalocyanine ◽  
Electron Paramagnetic

Singlet molecular oxygen produced in the presence of 2,2,6,6-tetramethyl-4-piperidone (TMPD) in 1,4-dioxan, by boron subphthalocyanine chloride as the sensitizer, was monitored by Electron Paramagnetic Resonance (EPR) via the oxidation of TMPD to the corresponding aminoxyl radical. This radical product is formed in low yields along the singlet oxygen pathway. A kinetic analysis of the process allows one to understand the reasons behind this, while affording more accurate quantitative insights into the mechanistic details. A crucial aspect of this reaction system, which explains the low aminoxyl radical yields along the singlet oxygen pathway, is the disappearance of the sensitizer triplet state in a reaction with TMPD, which has a rate constant of 1 × 109 M-1.s-1.

Electron Paramagnetic Resonance Study of Single Crystals of Horse Heart Ferricytochrome c at 4.2 °K

1972 ◽  
Vol 50 (10) ◽  
pp. 1048-1055 ◽  
Author(s):  
Colin Mailer ◽  
C. P. S. Taylor
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Single Crystals ◽  
Electron Paramagnetic Resonance Study ◽  
Field Potential ◽  
Personal Communication ◽  
Chem Phys ◽  
Paramagnetic Resonance ◽  
Ferricytochrome C ◽  
G Value ◽  
Electron Paramagnetic

Electron paramagnetic resonance (E.P.R.) spectra from single crystals of horse heart ferricytochrome c at 4.2 °K were analyzed to obtain the orientation of the principal g values relative to the crystallographic axes. The axis of the largest principal g value (g3 = 3.06) was within 5° of the heme normal direction reported in the X-ray structure of the same crystals (Dickerson et al.: J. Biol. Chem. 246, 1511 (1971)). The other two g axes (g1 = 1.25, g2 = 2.25) lie within 5° of the N–Fe–N directions in the heme ring, in contrast to met-myoglobin azide (Helcké et al.: Proc. R. Soc. B169, 275 (1968)) and cyanide (Blumberg, W. E.: personal communication) where they lie ~ 45° from the N–Fe–N directions. A version of Eisenberger and Pershan's theory (J. Chem. Phys. 47, 327 (1967)) was used to explain the 400–2000 G variation in linewidth on crystal rotation. The results were explained by combining the broadening produced by a distribution of rhombic crystal field potential (r.m.s. deviation 11%) over the molecular population, with that from a variation in the directions of the principal g values caused by misorientation (r.m.s. deviation 1.5°) of the molecules in the crystal.

Electrically Detected Magnetic Resonance On GaAs/AIGaAs Heterostructures

1996 ◽  
Vol 442 ◽  
Author(s):  
T. Wimbauer ◽  
D. M. Hofmann ◽  
B. K. Meyer ◽  
M. S. Brandt ◽  
T. Brandl ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Surface Defects ◽  
Electrical Contact ◽  
Paramagnetic Resonance ◽  
Quantum Well Structures ◽  
Carrier Recombination ◽  
Electrically Detected Magnetic Resonance ◽  
Antisite Defects ◽  
G Value ◽  
Electron Paramagnetic

AbstractElectrically detected magnetic resonance (EDMR) has been used to study carrier recombination in GaAs/AlGaAs quantum well structures grown by molecular beam epitaxy. The spin dependent photoconductivity signals depend strongly on the electrical contact properties. Using silver paste contacts a narrow (18 G) resonance located at g = 2.001 is observed. It has been previously attributed to surface defects on GaAs. Using alloyed In-contacts other signals are detected. The dominant resonance observed at 9 GHz has an isotropic g-value of g = 1.99 with a halfwidth of 200 G and is therefore assigned to Cr4+. Other signals of considerably lower intensity are explained by the well known electron paramagnetic resonance (EPR) properties of the Gai-interstitial and the AsGa-antisite defects. EDMR performed at 34 GHz allows the experimental separation of the two sets of hyperfine lines.

Electron paramagnetic resonance characterization and conformation of daunorubicin semiquinone intermediate implicated in anthracycline metabolism, cardiotoxicity, and anticancer action

1981 ◽  
Vol 59 (22) ◽  
pp. 3212-3217 ◽  
Author(s):  
J. William Lown ◽  
Hsiao-Hsiung Chen
Keyword(s):  
Aqueous Solution ◽  
Antitumor Antibiotic ◽  
Epr Spectrum ◽  
Paramagnetic Resonance ◽  
Acetyl Group ◽  
G Value ◽  
The Individual ◽  
Electron Paramagnetic ◽  
Spin Densities ◽  
Good Agreement

The antitumor antibiotic daunorubicin, upon reduction in aqueous solution, gives a transient resolved epr spectrum of linewidth 17.0 G and g value of 2.0024. This is ascribed to the semiquinone previously tentatively assigned in the unresolved epr spectrum obtained by microsomal activation of the antibiotic. By reference to the epr spectrum of quinizarin semiquinone in aqueous solution the individual proton hyperfine splitting constants in both spectra were tentatively assigned by computer simulation. LCAO–MO calculations of one-electron wave function spin densities in both species gave good agreement between calculated and observed hfs for values of the parameters βCO/βCC = 1.8, δα = 1.4, allowing definite assignment of the aromatic protons. By considering the angular dependence of the ring A benzylic proton hfs it was possible to discriminate between two alternative half-chair conformations of daunorubicin semiquinone. The preferred conformation of the intermediate is tentatively assigned as that which places both 7 and 9 oxygen functions equatorial and the C-9 acetyl group axial.

EFFECT OF IONIC RADIUS OF THE A SITE ON EPR LINE IN PARAMAGNETIC AND FERROMAGNETIC PHASE OF La0.7-xRxCa0.3MnO3

2001 ◽  
Vol 15 (27) ◽  
pp. 3559-3568
Author(s):  
G. NARSINGA RAO ◽  
Y. BABU ◽  
M. D. SASTRY ◽  
D. SURESH BABU
Keyword(s):  
Line Width ◽  
Ionic Radius ◽  
Bond Angle ◽  
Partial Substitution ◽  
Ferromagnetic Phase ◽  
Paramagnetic Resonance ◽  
Lanthanide Element ◽  
G Value ◽  
A Site ◽  
Electron Paramagnetic

The effects of partial substitution of La by a smaller Lanthanide element (R) in La 0.7-x R x Ca 0.3 MnO 3 ( R = Ce , Pr, Nd Sm, Gd, Dy with x = 0 and 0.1) ceramic pellets on the electron paramagnetic resonance has been investigated. The line width increased with decrease in ionic radius of the A site <r A > in paramagnetic phase, which is explained on the basis of tolerance factor. The observed increase in g-value and line width with increase in <r A > in ferromagnetic phase explained qualitatively by Mn-O-Mn bond angle distortion and Mn-O orbital overlap which in turn is governed by the size of the substitution ion.

scholarly journals EPR study of NO radicals encased in modified open C<sub>60</sub> fullerenes

2020 ◽  
Vol 1 (2) ◽  
pp. 197-207
Author(s):  
Klaus-Peter Dinse ◽  
Tatsuhisa Kato ◽  
Shota Hasegawa ◽  
Yoshifumi Hashikawa ◽  
Yasujiro Murata ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Relaxation Times ◽  
Three Dimensional ◽  
Activation Temperature ◽  
Paramagnetic Resonance ◽  
Yield Information ◽  
G Value ◽  
Pulsed Electron Paramagnetic Resonance ◽  
Electron Paramagnetic ◽  
Partial Compensation

Abstract. Using pulsed electron paramagnetic resonance (EPR) techniques, the low-temperature magnetic properties of the NO radical being confined in two different modified open C60-derived cages are determined. It is found that the smallest principal g value g3, being assigned to the axis of the radical, deviates strongly from the free electron value. This behaviour results from partial compensation of the spin and orbital contributions to the g3 value. The measured g3 values in the range of 0.7 yield information about the deviation of the locking potential for the encaged NO from axial symmetry. The estimated 17 meV asymmetry is quite small compared to the situation found for the same radical in polycrystalline or amorphous matrices ranging from 300 to 500 meV. The analysis of the temperature dependence of spin relaxation times resulted in an activation temperature of about 3 K, assigned to temperature-activated motion of the NO within the modified open C60-derived cages with coupled rotational and translational degrees of freedom in a complicated three-dimensional locking potential.

Investigations of the Gyromagnetic Factors for the Ni3+ Center in MgO

2010 ◽  
Vol 303-304 ◽  
pp. 113-116
Author(s):  
Xue Mei Li
Keyword(s):  
Local Structure ◽  
Relative Elongation ◽  
Impurity Center ◽  
Theoretical Calculations ◽  
Paramagnetic Resonance ◽  
Jahn Teller ◽  
Jahn Teller Effect ◽  
G Value ◽  
Electron Paramagnetic ◽  
Good Agreement

The electron paramagnetic resonance (EPR) gyromagnetic factors for the Ni3+ center in MgO are theoretically investigated using the improved g formulas for a tetragonally elongated octahedral 3d7 complex suffering the dynamical Jahn-Teller effect. From the studies, the impurity Ni3+ center is found to undergo the relative elongation along the tetragonal axis by about 1%. The calculated g value shows good agreement with the observed result, and the improvement in the theoretical calculations is achieved in this work as compared with the previous treatments. The local structure of the impurity center is discussed.

Electron paramagnetic resonance studies on copper(II) benzoate

1969 ◽  
Vol 47 (4) ◽  
pp. 555-557 ◽  
Author(s):  
F. G. Herring ◽  
R. C. Thompson ◽  
C. F. Schwerdtfeger
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Magnetic Susceptibility ◽  
Polycrystalline Copper ◽  
Spin Hamiltonian ◽  
Paramagnetic Resonance ◽  
Binuclear Molecule ◽  
G Value ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic

An electron paramagnetic resonance (e.p.r.) study at 9.1 and 12.0 GHz on polycrystalline copper(II) benzoate has given the following Spin Hamiltonian parameters for the binuclear molecule: D = 0.3311 ± 0.0006 cm−1, E = 0.0147 ± 0.0003 cm−1, gx = 2.048 ± 0.004, gy = 2.074 ± 0.004, gz = 2.345 ± 0.004. Using the average g value of 2.160 ± 0.004 obtained from e.p.r. and previously published magnetic susceptibility studies, 2J is estimated to be 333 cm−1.

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