Abstract

Multiple-quantum coherences (MQC) are used in a wide variety of solid-state NMR techniques for determining molecular structure. The dipolar couplings that are required for creating MQC vanish under magic-angle-spinning conditions, necessitating the use of dipolar recoupling techniques. Most recoupling sequences used to date, achieve "double-quantum recoupling" (e.g., C7); when applied to an ensemble of multi-spin systems at thermal equilibrium, they sequentially convert longitudinal magnetization into MQC of even orders, i.e., 2,4,6,...

Based on the CN [1] and RN [2] families of pulse sequences, we present novel recoupling methods for the following purposes:

(1) "Single-quantum recoupling" [3,4]. Such sequences create MQC orders in steps of 1, i.e., convert longitudinal magnetization into coherence orders 1,2,3,.... They are useful for spin-counting purposes.

(2) "Triple-quantum recoupling" [5], leading to excitation of MQC orders in steps of 3.

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