Abstract
Hyperpolarization techniques such as dynamic nuclear polarization (DNP), chemically induced dynamic nuclear polarization (CIDNP), and parahydrogen-induced polarization (PHIP) enhance the sensitivity of NMR spectroscopy and MRI, but the associated antiphase magnetization patterns often relax faster than those of conventional in-phase signals. This study analyzes the spin–lattice relaxation matrix for single-quantum transitions in an isolated, weakly coupled two-spin AX system to identify eigenvectors and eigenvalues that govern the time evolution of in-phase and antiphase longitudinal magnetization. The analysis predicts that AX antiphase magnetization, such as that generated by PHIP hydrogenations in high magnetic field, can relax up to twice as fast as the in-phase magnetization of traditional inversion-recovery or saturation-recovery experiments. To validate these predictions, a dedicated NMR pulse sequence was used to selectively generate and monitor antiphase magnetization. trans-Cinnamic acid in deuterated DMSO served as a model compound, with the hydrogen atoms on its central conjugated double bond forming a weakly coupled AX spin system with a large scalar coupling (>16 Hz). The large scalar coupling allowed for the separate integration of the two lines in each doublet. Experimental results confirm an accelerated relaxation of antiphase magnetization but also reveal that in-phase relaxation is influenced by double-quantum transitions, which do not contribute to the relaxation of antiphase magnetization. The findings of this study highlight the importance of distinguishing in-phase from antiphase relaxation, providing a basis for optimizing hyperpolarization experiments with explicit consideration of antiphase signal dynamics.
Recommended Citation
L. M. Kehoe et al., "Revisiting the Spin–Lattice Relaxation of Homonuclear In-Phase and Antiphase NMR Magnetization," Journal of Physical Chemistry A, vol. 129, no. 39, pp. 8993 - 9000, American Chemical Society, Oct 2025.
The definitive version is available at https://doi.org/10.1021/acs.jpca.5c05247
Department(s)
Chemistry
International Standard Serial Number (ISSN)
1520-5215; 1089-5639
Document Type
Article - Journal
Document Version
Citation
File Type
text
Language(s)
English
Rights
© 2025 American Chemical Society, All rights reserved.
Publication Date
02 Oct 2025
PubMed ID
40987608
Included in
Materials Chemistry Commons, Online and Distance Education Commons, Physical Chemistry Commons, Scholarship of Teaching and Learning Commons, Science and Mathematics Education Commons
Comments
Missouri University of Science and Technology, Grant None