Two-Dimensional (2D) NMR Methods

5 Coherence Transfer Pathways

David E. Korenchan¹ and Alexej Jerschow²

¹ Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, Massachusetts, United States of America ² Department of Chemistry, New York University, New York, NY 10003, USA

The product operator formalism discussed in Chapter 3 represents a powerful tool for a detailed description of the evolution of magnetization modes during an NMR pulse sequence. In this chapter, we discuss coherence transfer pathways (CTPs), which represent a more abstract concept for describing pulse sequences. CTP selection can be applied in many cases in which the use of the product operator formulation is too difficult or impossible. We discuss here the main methods used in coherence pathway selection, phase cycling and pulsed gradients, and we provide examples of how these are implemented in important classes of experiments.

5.1 Coherence Transfer Pathways: What and Why?

Directly detectable NMR signals arise only from very specific coherences between spin states. It was the discovery of controlled coherence conversions between detectable and undetectable coherences [1] that led to the rapid development of multi-dimensional and advanced NMR techniques [2]. Often, an important ingredient of experiments is the evolution of different magnetization modes under specific interactions, such that signal modulations can be read out indirectly even from modes that are not directly detectable. Such evolution ...