Standard longitudinal relaxation time

Fig. 5. Plot of the logarithm of the standard rate constant for electroreduction of Mn(AcAc)3 (A) and Fe(AcAc)3 ( ) in a given solvent against the logarithm of the longitudinal relaxation time of the solvent [177], The left-hand ordinate scale applies of the Mn system and the right-hand scale of the Fe system. BTN, butyronitrile for definition of the other solvents see Table 1.

Fig. 6. Dependence of the logarithm of the standard rate constant of phenothiazine oxidation on a Ft electrode on the logarithm of the solvent s longitudinal relaxation time. NE, nitroethane TMS, sulfolane. For other abbreviations see 1k-blel.

Deuterium nuclei in water molecules have negligible asymmetry parameters and residual anisotropies. After correcting for the paramagnetic impurities present, that affect relaxation rates somewhat (35), one obtains from the experimental data a value of the longitudinal relaxation rate for the water deuterons in the bound state of 650 s 1. This value incorporates the quadrupolar coupling constant (above determined) and the correlation time for bound waters. Using the standard expression for quadrupolar relaxation (29,35) yields a value for t 1.6 ns. 

It should be pointed out that, if the electric and the magnetic field are collinear, the magnetic field has no influence on a quasi-free-electron gas (with the dispersion relation s(k) = h k /2m ). If a given material shows a longitudinal magnetoresistance, it is almost certain that the conduction band is not of the standard parabolic form. The qualification almost relates to the assumption that the relaxation time is... 

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