Second strong quadrupole interaction

A characteristic broadening of the central transition can be observed in the case of strong quadrupole interaction (second-order quadrupole broadening). The second moment, Mf of the central transition with respect to its center of gravity is given by [12] ... 

A second potential attribute is simply polarity. A compound designed for solubility in CO2 should contain some polar character, (e.g., dipoles capable of interacting with CO2 through its strong quadrupole moment). An important limitation here is that the compound should not be so polar such that solute-solute interactions dominate. 

The NMR spectra of quadrupole nuclei with half-integer nuclear spins 7> 1/2 consist of the central transition (CT), +1/2 <-> —1/2, and the so-called satellite transitions, ( 1/2 <-> 3/2), + 3/2<-> 5/2), etc. In the case of strong quadrupolar interactions, it is practically impossible to excite the whole spectrum non-selectively (i.e., the CT is often selectively observed). Therefore, the second moments, caused by quadrupolar interactions in Eqs. (6) and (10), are those of the CT only. 

If the quadrupole interaction is strong enough also the second-order perturbation term has to be taken into account. For nuclei with I = 3/2, the second-order correction to the energy shifts the central line in the spectrum. For an aligned sample the magnitude of the shift is given by... 

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