Theory of Localized Polarization Transfer

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Abstract
Because polarization transfer from one type of nucleus to another can occur only when both types of nuclei are excited, it is possible, by using two separate rf coils for the excitation, to restrict the spatial region of the sample from which a signal can be received to a specific volume of overlap of the two inhomogeneous field patterns. In this paper we develop the theory of this method of localization in a homogeneous static field. The polarization transfer is achieved by a generalized phase-cycled DEPT sequence, in which case the method has the additional advantage of a gain in sensitivity of a 13C signal associated with the maximum polarization-transfer enhancement. Localization by means of the inverse-DEPT sequence is also studied, and off-resonance effects are calculated. Experimental confirmation of the theoretical expressions is given.© 1985 Academic Press,Inc.