The intensities of NMR and EPR transitions

Because 0 (the p state lies below the a state), NJNp 1 and there are 

At resonance there is strong coupling between the electron spin and the radiation, and strong absorption occurs as the spins flip from p (low energy) to a (high energy). We refer to these transitions as electron paramagnetic resonance (EPR), or electron spin resonance (ESR), transitions. 

The behavior of nuclei is very similar. The energy separation of the two states of a spin- nucleus (Fig. 13.2) is 

Energy difference between the spin statesofanucieus in a magnetic fieid 

Because for nuclei with positive the a state lies below the p state, - 0 and it follows from eqn 13.9 that 1 there are slightly more a spins than p spins 

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