Nuclear spin solid-state interactions

It is usual in magnetic solids for the main influence on the Mdssbauer spectrum to be felt through the interactions [1] and [2]. That is, the nucleus senses its own atom and the state of the solid via the effect of the solid on that atom. The interactions of class [1] are (i) the magnetic hypeifine interaction between the atomic spin S and the nuclear spin /, (ii) the interaction between the nuclear quadrupole moment Q (which is proportional to the deviation from a spherical distribution of nuclear charge) and the electric field gradient (EFG) produced by the electronic charge distribution of the atom, and (iii) the electrostatic interaction of the... 

Figure Bl.15.3. Typical magnitudes of interactions of electron and nuclear spins in the solid state (logarithmic scale).

NMR spectroscopy is a powerful technique to study molecular structure, order, and dynamics. Because of the anisotropy of the interactions of nuclear spins with each other and with their environment via dipolar, chemical shift, and quadrupolar interactions, the NMR frequencies depend on the orientation of a given molecular unit relative to the external magnetic field. NMR spectroscopy is thus quite valuable to characterize partially oriented systems. Solid-state NMR... 

Although the same nuclear spin interactions are present in solid-state as in solution-state NMR, the manifestations of these effects are different because, in the solid, the anisotropic contribution to the spin interactions contributes large time-independent terms to the Hamiltonian that are absent in the liquid phase. Therefore, the experimental methods employed in solids differ from the ones in the liquid state. The spin Hamiltonian for organic or biological solids can be described in the usual rotating frame as the sum of the following interactions ... 

The NMR observables of a substance as a liquid, solution, or in the gas phase of paramount importance to the inorganic chemist are chemical shifts and nuclear spin-spin coupling constants. In the solid state, however, these effects generally are dwarfed by anisotropic dipolar interactions so... 

In the derivation of these spin-interaction selection rules the harmonic approximation was made. In taking nuclear vibration into account2,77 these selection rules are often broken. In addition to coupling with the internal vibrational modes of a molecule, coupling with the phonon modes in the solid state may be important.124 Some use of double point group symmetry will be found in Sections IX, XI, and XII. 

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