General Principles Quadrupole Moment, Relaxation, Linewidth

General Principles Quadrupole Moment, Relaxation, Linewidth 

The experiments we have so far described have been used to study nuclei with spin I = Vi H, 13C, 31P). Our model compounds 1 and 2 contain two further atoms (oxygen and chlorine), which have no NMR-active isotope with spin Vi. Oxygen does however have an NMR-active isotope with spin I = 5/2 but very low natural abundance (0.037%) this is 170. Chlorine has two NMR-active isotopes 35C1 (I = 3/2,75.53%) and 37Cl (I = 3/2,24.47%). 

NMR-active nuclei with spin Vi (these include, as we mentioned previously, deuterium) have an electric quadrupole moment and are thus referred to as quadrupolar nuclei. 

These nuclei (and they form by far the majority of the NMR-active nuclei ) are subject to relaxation mechanisms which involve interactions with the quadrupole moment. The relaxation times T2 and T2 (T2 is a second relaxation variable called the spin-spin relaxation time) of such nuclei are very short, so that very broad NMR lines are normally observed. The relaxation times, and the linewidths, depend on the symmetry of the electronic environment. If the charge distribution is spherically symmetrical the lines are sharp, but if it is ellipsoidal they are broad. 

Briefly, the experimental conditions should be based on the following information acetonitrile is the recommended solvent, as it gives sharper lines than 

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