Electron spin resonance measurements

Thermal analyses of the sodium salts of several sulphuroxyacids, including some non-isothermal kinetic data, have been reported [813], Evidence for the formation of SOi radicals during such reactions has been obtained [348] by electron spin resonance measurements. 

That this reaction occurs is shown by electron spin resonance measurements, which indicate the complete disappearance of radicals in the system immediately after the addition of monomer. The dimerization occurs to form the styryl dicarbanion instead of - CH2CH4>CH4>CH2 -, since the former is much more stable. The styryl dianions so-formed are colored red (the same as styryl monocarbanions formed via initiators such as n-butyl-lithium). Anionic propagation occurs at both carbanion ends of the styryl dianion... 

Electron Spin Resonance Measurements. The specimens used in the electron spin resonance (ESR) studies were prepared by immersing the... 

Chemical Changes. Electron Spin Resonance Measurements. Electron spin resonance (ESR) measurements were carried out to de-... 

Evidence for such stable free radicals has been obtained from electron spin resonance measurements. A sample of the 77-23 PVC-styrene, which had been exposed to 0.8 megarad of gamma-radiation at room temperature, displayed resonance peaks comparable to 3 X 10 8 mole per gram of free radicals (compared with a diphenyl picrylhydrazyl standard). When an identical sample was heated for 10 minutes at 75°C. following irradiation, the free radical population had fallen below detection limits. Heating evidently destroyed or decreased the free radical content by reaction or termination. 

We have also made some electron spin resonance measurements on one sample, CGL 256, before and after laboratory carbonization (I). The results were as follows ... 

H. Tschamler. Dr. E. de Ruiter and I have also made electron spin resonance measurements on macerals (E. de Ruiter and H. Tschamler, Brennstoff-Chem. 42, 290 (1961)). We found quite similar results for micrinites to the single value reported by Given et al. 

Few photochromes exhibit paramagnetism as evidenced by magnetic susceptibility and electron spin resonance measurements. In spite of this selectivity, these are probably the most powerful techniques to aid in the elucidation of mechanisms for certain photochromic systems. 

Electron spin resonance measurements at room temperature on poly(thienylpyrrole) showed an asymmetric line characteristic of conduction electrons, with a g value near that of the free electron indicating that the spin resonance is not due to the sulfur and/or nitrogen moieties. 

The electronic structure of tetrahedral oxyanions and their derivatives has been extensively studied by many authors during the past decades. The earlier attempts were summarized by Prins [1]. Since the work of Walsh [2] and that of Wolfsberg and Helmholz [3] several semi-empirical theoretical studies have been published [4-7]. Later ab initio [8-10] and scattered wave calculations [11] have been also reported. Among the experimental investigations, Prins mentioned the electron spin resonance measurements of radicals formed by ejection or addition of an electron from or to certain oxyanions, obtaining information on just those molecular orbitals which contained unpaired electrons. [12] X-ray absorption and emission studies provided usefial information on a limited number of molecular orbitals in the valence band [13-19]... 

Electron spin resonance measurements on thymine monoanion (triplet state) confirm the deprotonation of thymine from N -1 and/or N-3 atoms. 

Very little is known about the physical properties of carbon onions. Electron spin resonance measurements on macroscopic quantities of onions, with 3-10 nm sizes, show that these structures have a Pauli-like spin susceptibility close to that of graphite [181]. It demonstrates that carbon onions also belong to the family of conducting carbon structures. 

Irradiation of DNA in the solid state at liquid nitrogen temperature yields radicals in which, electron spin resonance measurements indicate, the unpaired spin is delocalized over the entire chain and does not belong to any one unit of the giant molecule. 

Titania sol and gel prepared through the hydrolysis of tetrabutyl titanate in acid water solution are sensitive to ultraviolet (UV) irradiation and turn into blue color [137]. Electron spin-resonance measurement showed that the pho-tochromism was ascribed to the presence of titanium (III) ions in the Ti-O-Ti network. The titanium (III) ions could be oxidized by the oxygen in the atmosphere, and then the sol and gel faded slowly. The absorption peaks in the optical absorption spectra of the titania gel were attributed to the transition of 3-dimensional electrons of a trivalent titanium in certain environments. 

Arrhenius plots demonstrating the effect of temperature on lettuce seed aging rate (squares) and on molecular mobility calculated using the Adam-Gibbs model and heat capacity measurements (open circles) and from rotational motion using electron spin resonance measurements. Data are from Walters et al., (2004) (aging rate), Walters, (2004) (glass relaxation rates) and Buitink et al., (2000) (ESR measurements). 

In situ electron-spin resonance measurements enable the qualitative and quantitative detection of ion-radicals, and tracking of their relaxation dynamics. 

This initiation process is thus similar to alkali metal initiation in (a). That this reaction occurs is shown by electron spin resonance measurements, which indicate the complete disappearance of radicals in the system immediately after the addition of monomer. The monomer in these systems often has a lower electron affinity than the polycyclic hydrocarbon, but dimerization of the monomeric radical anion [Eq. (8.15)] drives the equilibrium of reaction (8.14) to the right. Dimerization of radical centers is highly favored by their high concentrations, typically 10 -10 M and the large rate con-stants (10 -10 L/mol-s) for radical coupling. (Note that the dimerization occurs to form the styryl dicarbanion instead of CH2CH0CH0CH2 , since the former is much more stable.) The styryl dianions are colored red (the same as styryl monocarbanions formed via initiators such as n-butyllithium). Anionic propagation occurs at both carbanion ends of the styryl dianion ... 

The superconducting oxides La gSr 2Cu04 and I YCujOy were prepared by decomposition of mixed metal nitrates. Thermogravimetric analysis and electron spin resonance measurements indicated the presence of Cu(I) and Cu(III) in the Lai.8Sr.2 u 4 phase. The compound I YC C prepared from the nitrates and subjected to an oxygen anneal at 425°C gave a sharp superconducting transition at 92 K. The phase was stoichiometric but readily decomposed when kept in contact with moist air. 

Electron-spin resonance measurements indicate this product to be a radical complex for which isotopic investigations suggest the structure (219) ... 

R. Vasquez, J. Avalos, F. Volino, M. Pineri, D. Galland, Electron spin resonance measurements of Cu++ distribution in cation exchange membranes, J. Appl. Polym. Sci., 1983, 28, 1093-1103. 

At room tenqrerature, the life-time of the transient species is generally very small. However, in the solid state at sufficiently low tenqrerature (77 K) tte reaction of transients can be slowed down so much that they can be obsmed over poiods of minutes or hours and could be conveniently studied tty optical absorption investigations in glassy matrix of 3-meth )entane (3MP), 2-metityhetrahydrofiiran and by electron spin resonance measurements [44-50]. With the availability of pulse ladiolysis technique, the idoitity of transients can be investigated at room temperature [29-39]. 

The first to be isolated of those complexes which enzymes form with their substrates was the complex of D-alanine, D-amino acid oxidase, and its co-factor FAD (riboflavine adenine dinucleotide). It consisted of hexagonal purple crystals and was stable in the absence of air. Electron spin resonance measurements showed that the co-factor, present in these crystals, was in its free-radical monohydro-form (FADH) (Yagi, 1965). 

Studies in radiation biochemistry have shown that there is some localization of free radical damage to enzymes and proteins at their sulfur amino acids. In proteins irradiated in solution cysteine, cystine and methionine arc some of the most labile amino acids. Radiation in the dry state allows electron spin resonance measurements and Gordy (1958) has shown the localization of unpaired electrons at sulfur in amino acids and proteins. As described previously in this article, in the damage to cytochrome c by linolenate peroxidation, cystine and methionine are among the most labile amino acids. If damage is localized at a sulfhydryl site on a protein, immediate molecular repair is possible by a sulfur interchange of the unpaired electron,... 

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