Nuclear spin coupling cases

In case (a) coupling two main possibilities arise. The first, which is expected to arise very rarely, if at all, implies that the magnetic interaction of the nuclear spin magnetic moment with the electronic orbital and spin moments is sufficiently strong to force the nuclear spin to be quantised in the molecular axis system. The basis kets may be expressed in the form rj, A S, S, A, 2 2, Iz, 2 2, N, J) this scheme is known 

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Coupling constant J (Section 13 7) A measure of the extent to which two nuclear spins are coupled In the simplest cases It IS equal to the distance between adjacent peaks in a split NMR signal... 

A nucleus under study by nuclear magnetic resonance techniques is affected by other nuclei in the same molecule. This phenomenon is known as spin-spin coupling. The effect arises (in adjacent nuclei) from the two electrons joining the nuclei in a covalent bond. Suppose the energy of states in which the electrons in the bond have opposing spins is lower than the state in which the electron spins are parallel. Then the AE between the two states (in this case a negative number) is called the coupling constant, J, expressed in frequency units, Hz. Internuclear... 

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