An analysis of liquid state cross polarization in AXNspin systems is presented. A twohyphen;level geometrical formalism derived from symmetry considerations provides a closed form description of the quantum dynamics for arbitraryN. A parallel discussion using a classical vector model explains the significance of the quantum mechanical solutions and illustrates the nature of the spinndash;spin correlations accompanying magnetization transfer. General expressions for theJcross polarization A signal with and without X decoupling are given. A discussion of RJCP and PCJCP pulse sequences introduced previously shows how manipulation of Hartmannndash;Hahn mismatch can advantageously modify crosshyphen;polarization dynamics. The quantum formalism demonstrates that efficient polarization transfer is equivalent to population inversion of an ensemble of fictitious spins subjected to different rf field intensities, and that pulse sequences for cross polarization can be constructed by analogy with conventional spin inversion techniques.
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