Radical-induced hetero-nuclear mixing and low-field 13C relaxation in solid pyruvic acid

Kouřilová, Hana; Jurkutat, Michael; Peat, David; Kouřil, Karel; Khan, Alixander S.; Horsewill, Anthony J.; MacDonald, James F.; Owers-Bradley, John; Meier, Benno

Abstract

Radicals serve as a source of polarization in dynamic nuclear polarization, but may also act as polarization sink, in particular at low field. Additionally, if the couplings between the electron spins and different nuclear reservoirs are stronger than any of the reservoirs’ couplings to the lattice, radicals can mediate hetero-nuclear polarization transfer. Here, we report radical-enhanced 13C relaxation in pyruvic acid doped with trityl. Up to 40 K, we find a linear carbon T1 field dependence between 5 mT and 2 T. We model the dependence quantitatively, and find that the presence of trityl accelerates direct hetero-nuclear polarization transfer at low fields, while at higher fields 13C relaxation is diffusion limited. Measurements of hetero-nuclear polarization transfer up to 600 mT confirm the predicted radical-mediated proton–carbon mixing.

Citation

Kouřilová, H., Jurkutat, M., Peat, D., Kouřil, K., Khan, A. S., Horsewill, A. J., …Meier, B. (2022). Radical-induced hetero-nuclear mixing and low-field 13C relaxation in solid pyruvic acid. Physical Chemistry Chemical Physics, 24(46), 28242-28249. https://doi.org/10.1039/D2CP04535D

• Journal Article Type: Article
• Acceptance Date: Nov 9, 2022
• Online Publication Date: Nov 14, 2022
• Publication Date: Dec 14, 2022
• Deposit Date: Dec 22, 2022
• Publicly Available Date: Dec 22, 2022
• Journal: Physical Chemistry Chemical Physics
• Print ISSN: 1463-9076
• Electronic ISSN: 1463-9084
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 24
• Issue: 46
• Pages: 28242-28249
• DOI: https://doi.org/10.1039/D2CP04535D
• Keywords: Physical and Theoretical Chemistry, General Physics and Astronomy
• Public URL: https://nottingham-repository.worktribe.com/output/14305041
• Publisher URL: https://pubs.rsc.org/en/content/articlelanding/2022/CP/D2CP04535D