Quadrupolar nuclei, physics

A. Samoson, E. Lippmaa, Excitation phenomena and line-intensities in high-resolution NMR powder spectra of half-integer quadrupolar nuclei, Physical Review B 1983, 28, 6567. 

Once an approximation to the wavefunction of a molecule has been found, it can be used to calculate the probable result of many physical measurements and hence to predict properties such as a molecular hexadecapole moment or the electric field gradient at a quadrupolar nucleus. For many workers in the field, this is the primary objective for performing quantum-mechanical calculations. But from... 

The values of T range broadly, depending on the particular type of nucleus, the location of the nucleus (atom) within a molecule, the size of the molecule, the physical state of the sample (solid or liquid), and the temperature. For liquids or solutions, values of 10 2 102 s are typical, though some quadrupolar nuclei have (faster) relaxation times of the order of 1(H s. For crystalline solids, T values are much longer (Section 2.5). For now, just remember that the larger the value of 7j, the longer it takes for a collection of nuclei to reach (or return to) equilibrium. 

We begin, in Section 2, with a detailed theoretical examination of the physics of quadrupolar, spin-5 nuclei, using the matrix operator formalism to discuss the various NMR experiments used in biological spectroscopy of quadrupolar ions and the biexponential relaxation of these ions. The effect of interaction of the Rb+ ion with its chemical environment on relaxation characteristics of the 87 Rb nucleus is considered in Section 3. Section 4 deals with methods of differentiating between intra- and extracellular species of ions. In Section 5 we discuss the kinetics of Rb+ in a variety of tissues, as studied by 87Rb NMR. Where appropriate, studies of 23Na and 39K are also cited. 

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