Dynamics of $I = {3 \over 2}$ nuclei in isotropic slow motion, anisotropic and partially ordered phases

Abstract

NMR of quadrupolar nuclei, and, in particular 23 Na in soft tissues has attracted renewed interest due to the importance that sodium plays in physiology. The quadrupolar coupling and relaxation dynamics, including the appearance of the dynamic frequency shift are treated in this article. The equations governing irreducible spherical tensor analysis are derived and discussed. Experiments are shown to demonstrate how parameters such as the correlation time, the instantaneous and the residual quadrupolar couplings can be extracted from the data. Such experiments and procedures are particularly useful in the analysis of 23 Na NMR data from tissues or cell suspensions.

Observing different modes of mobility in lithium titanate spinel by nuclear magnetic resonance

“…Instead, consistent with molecular dynamics simulations, 19 this suggests microscopic Li hopping between a limited number of sites on a much shorter timescale than the experimentally accessible timescale of $10 À5 s, causing a partial, anisotropic averaging of the individual EFGs. This results in an experimentally observed residual quadrupolar coupling, [49][50][51] which is illustrated in Fig. 6.…”

Probing the microscopic environment of 23Na ions in brain tissue by MRI: On the accuracy of different sampling schemes for the determination of rapid, biexponential decay at low signal‐to‐noise ratio

“…Due to the electric quadrupole moment, the 23 Na nucleus experiences a strong interaction with local electric field gradients arising from the microscopic environment, e.g., close‐by proteins . This interaction results in a rapid biexponential decay of the NMR signal in the order of a few milliseconds (short/long component / ≈ 0.2–5.0 ms / 10–64 ms; cf.…”

Quadrupole sensitive pulse for signal filtering

“…On the one hand, that problem can be solved using smaller values of κ (κ = 1.25, 1.5, 1.75), because the strongest dependence of $\overline{CT}$ on κ is in the range κ ∈(1:2). On the other hand, under the condition when the total time of the pulse τ p ~ T 2 , the relaxation has a strong influence on the magnetization during the pulse and it leads to results which diverge from simulations 30 . The most natural solution of the relaxation problem would be changing the rf-field strength of adjacent pulses and not the total length of QSP by changing κ.…”