Spin-uncoupling ground states

Another important concept which emerges from this example is that of spin recoupling. The ground state of N(2p ) is Sy, in which the spins of the three valence electrons are coupled to give the maximum resultant, S =. As the H atoms approach, these spins uncouple from each other and form three pair bonds. In many cases, this kind of recoupling has been found to occur over a very short range of internuclear distances (0.5-1 bohr), and is frequently associated with a maximum in the potential surface (see Section III). 

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