ABSTRACT
The Brownian motion in liquid samples averages the through - space effect of nuclear magnets to zero. However, in solutions of POCl2F, for example, the phosphorus nucleus gives two resonances whose separation does not depend upon the magnetic field strength. (The chlorine nuclei (I = 3/2) have no effect. This is explained in Chapter 4.) The two resonances correspond to the two spin orientations of the fluorine nucleus so that the nuclei are nevertheless able to sense one another’s magnetic fields. Theoretical considerations show that the interaction occurs via the bonding electrons. The contact between one nucleus and its s electrons perturbs the electronic orbitals around the atom and so carries information about the nuclear energy to other nearby nuclei in the molecule and perturbs their nuclear frequency. The effect is mutual and in POCl2F both the fluorine(I = 1/2) and the phosphorus (I = 1/2) resonances are split into doublets of equal hertz separation. The magnitude of the effect for a particular pair of nuclei depends on the following factors:
