Off-resonance NOVEL
Name
JCPSA6-000147-164201_1.pdf
Description
Published version
Size
712.91 KB
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Adobe PDF
Checksum (MD5)
43d1cd5701fecd8d7a62d020559dfcd4
Author(s)
Jain, Sheetal Kumar
Mathies, Guinevere
Griffin, Robert Guy
Date Issued
October 2017
Journal
Journal of Chemical Physics
Publisher
AIP Publishing
Citation
Jain, Sheetal K., Guinevere Mathies, and Robert G. Griffin, "Off-resonance NOVEL." Journal of Chemical Physics 147, 16 (Oct. 2017): no. 164201 doi 10.1063/1.5000528 ©2017 Author(s)
Version
Final published version
Abstract
Dynamic nuclear polarization (DNP) is theoretically able to enhance the signal in nuclear magnetic resonance (NMR) experiments by a factor γ[subscript e]/γ[subscript n], where γ's are the gyromagnetic ratios of an electron and a nuclear spin. However, DNP enhancements currently achieved in high-field, high-resolution biomolecular magic-angle spinning NMR are well below this limit because the continuous-wave DNP mechanisms employed in these experiments scale as ω[superscript -n over subscript 0] where n ∼ 1-2. In pulsed DNP methods, such as nuclear orientation via electron spin-locking (NOVEL), the DNP efficiency is independent of the strength of the main magnetic field. Hence, these methods represent a viable alternative approach for enhancing nuclear signals. At 0.35 T, the NOVEL scheme was demonstrated to be efficient in samples doped with stable radicals, generating [superscript 1]H NMR enhancements of ∼430. However, an impediment in the implementation of NOVEL at high fields is the requirement of sufficient microwave power to fulfill the on-resonance matching condition, ω0I = ω1S, where ω[subscript 0I] and ω[subscript 1S] are the nuclear Larmor and electron Rabi frequencies, respectively. Here, we exploit a generalized matching condition, which states that the effective Rabi frequency, ω[superscript eff over subscript 1S], matches ω[subscript 0I]. By using this generalized off-resonance matching condition, we generate [superscript 1]H NMR signal enhancement factors of 266 (∼70% of the on-resonance NOVEL enhancement) with ω[subscript 1S]/2π = 5 MHz. We investigate experimentally the conditions for optimal transfer of polarization from electrons to [superscript 1]H both for the NOVEL mechanism and the solid-effect mechanism and provide a unified theoretical description for these two historically distinct forms of DNP.
MIT Department
Massachusetts Institute of Technology. Department of Chemistry
Francis Bitter Magnet Laboratory (Massachusetts Institute of Technology)
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DOI of Published Version
https://doi.org/10.1063/1.5000528
