Electron spin resonance ESR data

The electron spin resonance (ESR) method has been used to analyze the presence and localization, particularly of transition-metal ions, in heulandite-chnoptilolite series. 

An EPR study on and Cr ions introduced by solid- and liquid-state reactions with synthetic zeolites 3 A, 4A, 5 A, and the natural clinoptilolite was reported [96K2]. The coordination stracture around the Cu ions was found to be square pyramidal when solid-state reactions were used, whereas it is octahedral when the ions were introduced by the liquid-state reaction. In the above zeolites, Cr was oxidized to Cr, which coordination is square pyramidal. 

EPR studies were made on V0S04-3 H2O and MnCl2 2 H2O adsorbed on natural heulandite and clinoptilolite [96U1]. The spectra indicated that the coordination structirres were VOCHaO) and Mn(H20) +. The spectrum of V0(H20), at RT, displays an isotropic behavior and therefore the water ligands are mobile. By analyzing the spectra of Mn(H20)i in rratural heulandite and clinoptilolite only mobile water was formd. 

Ni aK-clinoptilolite showed O and P species due to the Nf-(NO) complex having axial symmetry - Table 8. The species Q, also with axial symmetry, was assigned to NO molecules adsorbed on the lattice. The 2-D ESEM study confirmed the Nf coordinations as above attributed. 

By ESR study of nickel catalysts supported on K-clinoptilolite containing iron, a correlation was fotmd between the Ni-Fe interaction and the resistance of the catalyst to thiophene poisoning [93 A2]. 

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II. STRUCTURAL CHARACTERISTICS A. Electron Spin Resonance (ESR) Data... 

Attempts to apply thermoluminescence (TL) and electron spin resonance (ESR) data to date soil horizons, and to use ESR to date bone are underway. As yet, there are no agreed-upon criteria on which to evaluate the overall reliability of age inferences based on ESR data (13). It has been suggested (14) that in some circumstances the obsidian hydration method can be used to infer chronological age over in excess of 100,000 years (14). However, obsidian is not a widespread natural resource and some of the hydration rate structures appear to yield problematic results. Amino acid racemization (AAR) values can be used under some conditions to infer accurate age values for bone, but seriously anomalous values can be obtained (15, 16). The conditions under which AAR values can be used to accurately infer age, particularly for bone samples, continue to be investigated. 

The role of the second plasma treatment by HFE or Ar seems to be the removal of type B plasma polymer of TMS from the top surface region or possibly converting the type B plasma polymer to type A plasma polymer. Electron spin resonance (ESR) data (described in Chapter 6) indicate that the number of Si-based dangling bonds decreases by these second plasma treatments. The weight loss observed with some plasma polymers and the ESR data for TMS film suggest that type B plasma polymer in the top surface region of an LCVD film could be up to nearly 30% of the... 

Electron spin resonance (ESR) data suggest that solution in pyridine does not significantly enhance the content of free radicals in humic substances. Pyridine does, however, significantly enhance their nitrogen contents (Table 5), especially in the cases of the fulvic acids, as was found also for extracts with EDA. Sorption, by ion-exchange and possibly by charge-transfer processes, might provide plausible explanations for the enrichments. 

A projection of Py2AsF6 is shown in Figure 9. It consists of two independent stacks with different setting angles but identical overlap (type 1). Because the crystal exhibits polysynthetic twinning, a full crystal structural analysis has not been undertaken. Preliminary data indicate that in a phase transition, both stacks become identical that is, the structure is face-centered in the low-temperature phase. This conclusion is supported by electron spin resonance (ESR) data. 

The electron spin resonance (ESR) technique has been extensively used to study paramagnetic species that exist on various solid surfaces. These species may be supported metal ions, surface defects, or adsorbed molecules, ions, etc. Of course, each surface entity must have one or more unpaired electrons. In addition, other factors such as spin-spin interactions, the crystal field interaction, and the relaxation time will have a significant effect upon the spectrum. The extent of information obtainable from ESR data varies from a simple confirmation that an unknown paramagnetic species is present to a detailed description of the bonding and orientation of the surface complex. Of particular importance to the catalytic chemist... 

The reactive intermediates mentioned above are initially ions and excited molecules and subsequently may be free radicals. Many ions are probably formed on irradiating PET, as judged by the large concentration of spins detected at —196°C. by electron spin resonance (ESR), but nothing is known directly about their chemical structure or reactivity. Any chemical role of excited molecules is equally a matter of conjecture. In these circumstances, the influence of dose rate will be discussed by reference to free radicals. Eventually, when more quantitative experimental data are obtained, the adequacy of free radical reactions may be better assessed, and the role of ions and excited molecules brought into perspective. 

There have been a large number of electron spin resonance (ESR) studies of coal and coal products,(1J but a microscopic interpretation of the resulting data has been hampered by the chemical heterogeneity of the coal samples examined. While several surveys of specially selected macerals have appeared, 3), the recent evolution of maceral separation techniques - now allows detailed ESR observations to be made on coals systematically fractionated in which coal rank, maceral type, and maceral density are simultaneously distinguished. The present report surveys the behavior of a variety of ESR properties of carbon radicals in exinite, vitrinite, and inertinite macerals in a variety of coals of different rank. These data... 

The data on electron spin resonance (ESR), electron-nuclear double resonance (ENDOR), and general triple resonance spectroscopy for 2,5-dihydro-l,2,3,5-thiatriazole-5-yl radicals was reviewed by Holm and Larsen <1996CHEC-II(4)733>. There are no new data on this subject. 

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