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International Journal of Spectroscopy
Volume 2016 (2016), Article ID 2390109, 9 pages
Review Article

The Heteronuclear Multiple-Quantum Correlation Experiment: Perspective from Classical Vectors, Nonclassical Vectors, and Product Operators

1Departamento de Farmacia, Instituto de Farmacia y Alimentos, Universidad de La Habana, Avenida 23, No. 21425 e/214 and 222, La Coronela, La Lisa, 13600 La Habana, Cuba
2Departamento de Química Física, Facultad de Química, Universidad de La Habana, Avenida Zapata y G, Vedado, 10400 La Habana, Cuba

Received 16 October 2015; Accepted 6 December 2015

Academic Editor: Guillermo Moyna

Copyright © 2016 Karen de la Vega-Hernández and Manuel Antuch. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


It is usually accepted that most 2D-NMR experiments cannot be approached using classical models. Instructors argue that Product Operators (PO) or density matrix formalisms are the only alternative to get insights into complex spin evolution for experiments involving Multiple-Quantum Coherence, such as the Heteronuclear Multiple-Quantum Correlation (HMQC) technique. Nevertheless, in recent years, several contributions have been published to provide vectorial descriptions for the HMQC taking PO formalism as the starting point. In this work we provide a graphical representation of the HMQC experiment, taking the basic elements of Bloch’s vector model as building blocks. This description bears an intuitive and comfortable understanding of spin evolution during the pulse sequence, for those who are novice in 2D-NMR. Finally, this classical vectorial depiction is tested against the PO formalism and nonclassical vectors, conveying the didactic advantage of shedding light on a single phenomenon from different perspectives. This comparative approach could be useful to introduce PO and nonclassical vectors for advanced upper-division undergraduate and graduate education.