Magnetic relaxation rates

Thus, the starting parameters for the computer-simulation of spectrum IB were chosen to agree with the value of hyperfine fields at 613 K as measured by Rlste and Tenzer, using neutron scattering measurements (36). In addition, the magnetic relaxation rate depends on temperature, as discussed in the Theory section of this paper. 

Some recent papers permit an exciting outlook on the degree of sophistication of experimental techniques and on the kind of data which may be available soon. In the field of NMR spectroscopy, a publication by Hertz and Raedle 172> deals with the hydration shell of the fluoride ion. From nuclear magnetic relaxation rates of 19F in 1M aqueous solutions of KF at room temperature, the authors were able to show that the orientation of the water molecules in the vicinity of fluoride ions is such that the two protons are non-equivalent. A geometry is proposed for the water coordination in the inner solvent shell of F corresponding to an almost linear H-bond and to an OF distance of approximately 2.76 A, at least under the conditions chosen. 

The pronounced increase above pH 9.3 of the proton nuclear-magnetic relaxation rates in aqueous solutions of (Cu",Zn )-BESOD at 295 K and 30 MHz was interpreted by the cleavage of His-61 from Cu and its replacement by an equatorial OH". The axial HjO on Cu remained unaffected... 

Cvi is the number of vinyl groups per chain. The direct observation of the decrease in amplitude of the Fourier Transform-Infrared spectroscopy (FT-IR) spectrum of vinyl groups leads to a square root dependence of a(t) on time. The threshold of gelation occurs at a time t0 such that e(t0) is equal to zero. Again, the magnetic relaxation rate is a function of the variable, e (Figure 8.4). 

Aisen, P., A. Leibman, and H. A. Reich Studies on the Binding of Iron to Transferrin and Conalbumin. J. Biol. Chem. 241, 1666 (1966). They have found by electrophoretic studies that the stability constants of the two binding sites in ovotransferrin and human serum transferrin are equivalent. By proton magnetic relaxation rate measurements, they also found that the binding sites of ovotransferrin and human serum transferrin acted independently. 

Figure 14 Measured relative molar shifts (a) 8 = the dielectric relaxation time, and (b) 8 = the intramolecular proton magnetic relaxation rate, of aqueous alkali-metal halide solutions these are plotted on the vertical axis against negative ion radii on the horizontal axis and against positive ion radii on the third axis...

Figure 1. Dispersion of 7/T/, the magnetic relaxation rate of solvent water protons, for a 65 mg/mL solution of alcohol-dehydrogenase from yeast, 160,000...

The copper/zinc- and manganese-containing superoxide dismutases are the only metalloproteins that are able to enhance the nuclear magnetic relaxation rate of F to an extent that makes this property detectable at the protein concentration usually present in most cells (Rigo et al., 1979). 

More recent NMR studies have questioned the concept of outer sphere coordination of substrate. Andersson et al. have suggested that the magnetic relaxation rate of solvent protons in solutions of LADH with Co" ions substituted specifeally for zinc at the catalytic site arises mainly from diamagnetic contributions, and the paramagnetic contributions are relatively small.This puts into doubt the conclusions of Sloan et al. and Drysdale and Hollis, who assumed paramagnetic contributions were predominant their results suggesting second sphere coordination of substrate may require some reinterpretation. N NMR has also been informative in this system. 

C, however, Ca + does not have a dehydrating effect on Li+ since these ions possess similar enthalpies of hydration in saturated aqueous solutions. The nuclear magnetic relaxation rates and shifts of Li+ and Cs+ in aqueous solutions containing Fe + and various counter-anions are interpreted in terms of a dipolar attraction between Li+ and the unpaired electrons on the Fe + ion, and the formation of an ion pair between Cs+ and ferric halide complex. An increase of pressure in the range 0—1000 bar results in an enhancement in the hydration of the ions Na+ and K+ in their aqueous chloride solutions. The enhancement is more pronounced at 20 than at 45 °C. These conclusions... 

Nuclear magnetic relaxation rates of in aqueous solution are markedly... 

Nuclear magnetic relaxation rates have been used to investigate the coordination number. In an investigation of the line-width broadening of La in various perchlorate solutions, Nakamura and Kawamura (1971) attributed the decreases in the values of (Av is the relaxation rate and is the relative viscosity) to a possible equilibrium between the nonahydrates and octahydrates for lanthanum ion. This conclusion was disputed by Reuben (1975) who proposed that this apparent anomaly reflected an erroneous estimate of the corrections of the linewidths for peaks due to the effect of the finite modulation amplitude and/or of partial saturation. Measurement of the transverse relaxation rates by the pulse method gave results consistent with a constant hydration number for lanthanum ion (Reuben 1975). 

It has been emphasized (Mock et al. 1986) that besides a systematic understanding of the occurrence or absence of elastic and phonon anomalies in different IV compounds the concept introduced above allows for a first experimental estimate of charge fluctuation rates. The direct experimental investigation of these has not been feasible, unlike the magnetic relaxation rates, which have been investigated intensively by quasielastic neutron scattering (Holland-Moritz et al. 

In this equation, a is the conductivity, A is a constant proportional to the number of carrier ions, B is a constant, and To is the temperature at which the configurational entropy of the polymer becomes zero and is close to the glass transition temperature (Tg). The VTF equation fits conductivity rather well over a broad temperature range extending from Tg to about Tg +100 K. Equation [3.2] is an adaptation of the William-Landel-Ferry WLF relationship developed to explain the temperature dependence of such polymer properties as viscosity, dielectric relaxation time and magnetic relaxation rate. The fact that this equation can be applied to conductivity implies that, as with these other properties, ionic... 

A further piece of supporting evidence is to be found by considering the entrancement factor 17 >vhich is the ratio of the actual nuclear magnetic relaxation rate to that calculated with the aid of the Korringa relationship. The model proposed by Mott predicts that r o and this is again found to be the case (Figure 7.22). 

Here Xt is the static susceptibility of the f-electron system, E is the magnetic relaxation rate of the f-state and Kff denotes the coupling constant of the spin of the ESR probe to the f moment via the indirect RKKY exchange. A schematic representation of the interactions which are described in eq. (34) and are responsible for the linewidth broadening in HFS is shown in fig. 41. 

Fig. 52. Magnetic relaxation rate r in URu2Si2 as calculated from the results shown in fig. 51. The solid line represents a square-root behavior. The inset shows the neutron scattering results r, T) which reveal a linear temperature dependence in a limited temperature range. From Spitzfaden et al. (1996).

Finally, AH(T) and the experimentally determined static susceptibilities have been used (Spitzfaden et al. 1996) to calculate the temperature dependence of the magnetic relaxation rates. The result is shown in fig. 52. Here r sR(J) is plotted in the paramagnetic regime and compared with the theoretical predictions by Cox et al. (1986) and Bickers et al. (1985). These authors predicted a square-root dependence of the magnetic relaxation rate for temperatures T >T. The inset of fig. 52. shows the magnetic relaxation rate as determined in inelastic neutron scattering experiments. In these experiments a linear temperature dependence has been observed, but only in a limited temperature range (Holland-Moritz et al. 1987). 

Boltzmann constant Gr magnetic relaxation rate from ion i to ion j... 

We are now able to write down the magnetic relaxation rates 1/T. as functions of the effective corre-(2) ... 

Diamagnetic electrolyte solutions Intermolecular nuclear magnetic relaxation rate of proton in water molecules correlation times for molecular rotation in free water and hydrated water self diffusion coefficients of water molecules 84, 85... 

NaF, KF, UbF, CsF F nuclear magnetic relaxation rates as a function of concentration models for hydration spheres self-diffusion of F in aqueous solution 87... 

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