Zero quantum transverse magnetization

Coherences, of which transverse magnetization is one example, can be classified according to a coherence order, p, which is an integer taking values 0, 1, 2. .. Single quantum coherence has p = 1, double has p = 2 and so on z-magnetization, "zz" terms and zero-quantum coherence have p = 0. This classification comes about by considering the phase which different coherences acquire is response to a rotation about the z-axis. 

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