Field dependence linewidth

Bucher et al. (1975) recorded the NMR spectra of PrS2. The spectra, which showed a rather complex feature field-dependent linewidth and frequency, that was not analyzed fiirther. 

Even for a single radical tire spectral resolution can be enlianced for disordered solid samples if the inliomogeneous linewidth is dominated by iimesolved hyperfme interactions. Whereas the hyperfme line broadening is not field dependent, tire anisotropic g-matrix contribution scales linearly with the external field. Thus, if the magnetic field is large enough, i.e. when the condition... 

Besides a poorly resolved triplet structure in the EPR spectrum of 57Fe enriched two-iron ferredoxins266 at gz, no hf interactions are observed in all these iron-sulfur clusters. The distribution of principal axes of the g tensors gives rise to an inhomogeneous, field-dependent EPR linewidth, and obscures the resolution of ligand hfs265. This distribution, whose origin is not completely established, does not, however, prevent application of the ENDOR technique. 

Eqs. 2, 3 and 4 can be used to simulate a powder spectrum, taking into consideration the correction for the transition probability necessary in a field-swept ESR spectrum" . In most cases an orientation dependent linewidth is assumed in generating the spectrum ... 

The hyperfine shifts of groups bound to the donor atom are largely dominated by the contact interaction, even if pseudocontact shift contributions are sizable and any quantitative use of the shifts should rely on the separated contributions. Longitudinal nuclear relaxation times can be used, and have been used in the case of cobalt substitute stellacyanin, to determine metal-proton distances [101]. The contribution of Curie relaxation, estimated from the field dependence of the linewidths, can be used both for assignment and to determine structural constrains [101]. 

Figure 5. The frequency-field (squares) and linewidth-field (circles) dependencies of the ESR excitations in CuGe03 at T= 4.2 K. The data are shown for ascending fields, B a. The dash line is a frequency-field dependence of magnetic excitations with g=2.15. The solid lines are guides for eyes. The dot line denotes the dimerized-incommensurate phase transition boundary.

Bain and co-workers [115] studied the field dependence of 13C linewidths for polyacrylates crosslinked to low levels. The linewidth was directly proportional to field strength, consistent with a significant contribution from a dispersion of chemical shifts arising from new chain structures. In addition the authors used the Delays Alternating with... 

The first term is the Curie spin term and the second term the usual dipolar expression. It follows that the Curie spin linewidth contribution should exhibit a field dependence of Bq and a temperature dependence of Since for Brownian diffusion ... 

It is worth noting that the linewidth of this resonance decreases with increasing Tc This behavior is in sharp contrast to the situation described by Eq. (2) and to the dipolar relaxation process, where the linewidth increases with increasing VqTc. From the field dependence of the chemical shift and linewidth described in Eqs. (3) and (4), the values of 7 and for spin 5/2 nuclei in the slow motion limit can be obtained. As the parameter % provides a measure of the coupling between the nuclear quadrupole and the electric field gradient at the nucleus, it reflects the symmetry of the local environment of the nucleus and thus can give information on the nature of the colloidal species, ic is a measure of the mobility of the species involved and, in principle, can provide information on the magnitude of the particle size when Eq. (1) is used. 

Upon rotating the magnetic field in the (011) plane of a single crystal of LaS doped with 2000 ppm Er, Bloch et al. (1982) found an angular-dependent linewidth. They assumed a T7 ground state of Er followed by a Tg excited state. Internal strains of Fs type are coupled to the lanthanide ions via magnetoelastic effects. The spin Hamiltonian... 

Section IV,B,2 introduces the idea that chemical-shift anisotropy could become an important relaxation mechanism for phosphorus at hi field. Vogel et al. (1982) have published the field dependence of the linewidth of the histidine 3-iV-phosphate of succinyl-CoA synthetase and the serine phosphate of glycogen phosphorylase a. They found that the CSA mechanism did, indeed, dominate at 6.3- and 9.3-T fields, contributed substantially at 4.7 T, and contributed about 25% of the total relaxation at 2.1 T (36.4 MHz). Vogel etal. 1982) estimated for Escherichia coli sucdnyl-CoA synthetase (MW 140,(XX)) a hydrated radius of 37 A and an isotropic correlation time of 44 ns. These numbers are referenced to the phosphorus linewidth (sensitive only to overall motion) using an analysis very similar to that mentioned in Section IV,B on DNA phosphorus relaxation. In contrast, the E. coli phosphoryl carrier protein HPr (MW 9(KX)) has a calculated hydrated radius of 17 A and a correlation time of 4.2 ns, according to Vogel et al. (1982). 

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