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Electron spin resonance linewidth

Electron spin resonance determinations of g-values, linewidths, radical densities and saturation properties have been performed on carbon radicals in samples of coal macerals isolated by density gradient centrifugation techniques. These data are compared with elemental analyses and density measurements. Each maceral type exhibits a different ESR signature" which can be understood in terms of the nature of the starting organic and the extent of coalification. [Pg.124]

Freed JH, Fraenkel GK (1963) Theory of linewidths in electron spin resonance spectra. J Chem Phys 39(2) 326... [Pg.194]

Detection of the conduction electrons by ESR is not feasible in the conductive Cu salts. Owing to the spin-orbit coupling and their pseudo-three-dimensional character (see below), the relaxation times are too short and therefore the linewidths too large [17]. There is thus an anticoincidence here between high conductivity and ESR [18]. In the one-dimensional conducting state of the li salts of DCNQI, with a smaller spin-orbit interaction, the electron-spin resonance can, in contrast, indeed be observed. [Pg.328]

The spectroscopy of electron spin resonance (ESR) is a means of detecting direct transitions between electron Zeeman levels. The phenomenon of electron spin resonance is observed only in atomic or molecular systems having net electron spin angular momentum, that is, materials containing one or more unpaired electrons. One of the most useful parameters that can be extracted from ESR spectra is the spectral linewidth this parameter provides information on rotating correlation time (re)." ... [Pg.103]

Alternatively, the spin susceptibility can be measured directly from the integrated intensity of the valence electron spin resonance (ESR). The ESR intensity is the integral of the imaginary part x"(Qy < >) over all Q and a> and is equal to 0). However, technical difficulties and large linewidths due to strong spin-orbit interactions have restricted ESR measurements to the simplest liquid metals, lithium and sodium, at temperatures close to their melting points (Enderby, Titman, and Wignall, 1964 Devine and Dupree, 1970). [Pg.57]

The oxidation (doping) process in the case of iodine has been monitored by electron spin resonance (esr) and optical spectroscopies. Esr reveals a narrowing of the initially broad signal at g 2.0 (AH 20G vs. 9G for cis- and 0.8G for trans-polyacetylene) Po lOG upon iodine vapor treatment. The number of spins increases with first order kinetics. In contrast, with polyacetylene there is no change in linewidth radical population decreases with first order kinetics. Optically, oxidation witl iodine causes the peak at 2eV (cf. 1.9eV for polyacetylene) to completely disappear and a new geak to appear at 0.9eV (Figure 3) (cf. 0.8eV for polyacetylene). [Pg.385]

The negative sign in equation (b 1.15.26) implies that, unlike the case for electron spins, states with larger magnetic quantum number have smaller energy for g O. In contrast to the g-value in EPR experiments, g is an inlierent property of the nucleus. NMR resonances are not easily detected in paramagnetic systems because of sensitivity problems and increased linewidths caused by the presence of unpaired electron spins. [Pg.1557]

The name ENDOR encompasses several types of experiments. The common feature in all ENDOR experiments is the simultaneous use of a microwave frequency to excite electron spin transitions and a RF to excite NMR transitions, hence the use of the term double resonance. ENDOR can be viewed as NMR spectroscopy detected via the electron spins. Smaller hyperfine couplings can be observed by ENDOR than by CW EPR because the linewidths of the ENDOR signals are orders of magnitude smaller than the widths of the EPR signals. [Pg.50]

Similarly to the ESR of the lanthanide ions in insulators, in metallic systems ESR contributes to understanding of the spectroscopic state of the ion in the host lattice and the symmetry and magnitude of the crystalline electric field at the lanthanide site. The g-shift of the resonance may be related to the sf exchange interaction and the spin polarization of the conduction electrons, and the temperature and concentration dependence of the g-shift and resonance linewidth relate to the bottleneck effect in the spin relaxation process. These relationships have been outlined in section 3.5. [Pg.493]


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See also in sourсe #XX -- [ Pg.276 , Pg.277 , Pg.289 , Pg.293 , Pg.303 , Pg.304 , Pg.370 , Pg.380 , Pg.704 ]

See also in sourсe #XX -- [ Pg.303 ]

See also in sourсe #XX -- [ Pg.91 ]




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