Preprints
https://doi.org/10.5194/mr-2021-25
https://doi.org/10.5194/mr-2021-25

  15 Mar 2021

15 Mar 2021

Review status: this preprint is currently under review for the journal MR.

Solid-State 1H Spin Polarimetry by 13CH3 Nuclear Magnetic Resonance

Stuart J. Elliott1,2, Quentin Stern1, and Sami Jannin1 Stuart J. Elliott et al.
  • 1Centre de Résonance Magnétique Nucléaire à Très Hauts Champs - FRE 2034 Université de Lyon/CNRS/Université Claude Bernard Lyon 1/ENS de Lyon, 5 Rue de la Doua, 69100 Villeurbanne, France
  • 2Department of Chemistry, University of Liverpool, Liverpool L69 7ZD, United Kingdom

Abstract. Dissolution-dynamic nuclear polarization is emerging as a promising means to prepare proton polarizations approaching unity. At present, 1H polarization quantification remains fastidious due to the requirement of measuring thermal equilibrium signals. Lineshape polarimetry of solid-state nuclear magnetic resonance spectra is used to determine a number of useful properties regarding the spin system under investigation. In the case of highly polarized nuclear spins, such as those prepared under the conditions of dissolution-dynamic nuclear polarization experiments, the absolute polarization of a particular isotopic species within the sample can be directly inferred from the characteristics of the corresponding resonance lineshape. In situations where direct measurements of polarization are complicated by deleterious phenomena, indirect estimates of polarization using coupled heteronuclear spins prove informative. We present a simple analysis of the 13C spectral lineshape asymmetry of [2-13C]sodium acetate based on relative peak intensities, which can be used to indirectly evaluate the proton polarization of the methyl group moiety, and very likely the entire sample in the case of rapid and homogeneous 1H-1H spin diffusion. 1H polarizations greater than ~10–25 % (depending on the sign of the microwave irradiation) were found to be linearly proportional to the 13C peak asymmetry, which responds differently to positive or negative microwave irradiation. These results suggest that, as a dopant, [2-13C]sodium acetate could be used to indirectly gauge 1H polarizations in standard sample formulations, which is potentially advantageous for: samples polarized in commercial dissolution-dynamic nuclear polarization devices that lack 1H radiofrequency hardware, measurements which are deleteriously influenced by radiation damping or complicated by the presence of large background signals, and situations where the acquisition of a thermal equilibrium spectrum is not feasible.

Stuart J. Elliott et al.

Status: open (until 02 May 2021)

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Stuart J. Elliott et al.

Stuart J. Elliott et al.

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Short summary
A straightforward lineshape analysis of the 13C spectral asymmetries of [2-13C]sodium acetate can be used to indirectly evaluate the 1H polarization of the CH3 group, and likely entire samples in the case of rapid and homogeneous 1H-1H spin diffusion. The results are potentially advantageous for polarizers that lack 1H radiofrequency hardware, measurements which are influenced by radiation damping or large background signals, or where acquisition of thermal equilibrium spectra are not feasible.