Off-resonance NOVEL

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JAIN, Sheetal K., Guinevere MATHIES, Robert G. GRIFFIN, 2017. Off-resonance NOVEL. In: The Journal of Chemical Physics. 147(16), 164201. ISSN 0021-9606. eISSN 1089-7690. Available under: doi: 10.1063/1.5000528

@article{Jain2017-10-28Offre-40823, title={Off-resonance NOVEL}, year={2017}, doi={10.1063/1.5000528}, number={16}, volume={147}, issn={0021-9606}, journal={The Journal of Chemical Physics}, author={Jain, Sheetal K. and Mathies, Guinevere and Griffin, Robert G.}, note={Article Number: 164201} }

Mathies, Guinevere eng 2017-10-28 Jain, Sheetal K. terms-of-use Griffin, Robert G. Dynamic nuclear polarization (DNP) is theoretically able to enhance the signal in nuclear magnetic resonance (NMR) experiments by a factor γ<sub>e</sub>/γ<sub>n</sub>, 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<sub>−n</sub><sup>0</sup> 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 1H 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, ω<sub>0I</sub> = ω<sub>1S</sub>, where ω<sub>0I</sub> and ω<sub>1S</sub> are the nuclear Larmor and electron Rabi frequencies, respectively. Here, we exploit a generalized matching condition, which states that the effective Rabi frequency, ω<sup>eff</sup><sub>1S</sub>, matches ω<sub>0I</sub>. By using this generalized off-resonance matching condition, we generate 1H NMR signal enhancement factors of 266 (~70% of the on-resonance NOVEL enhancement) with ω<sub>1S</sub>/2π = 5 MHz. We investigate experimentally the conditions for optimal transfer of polarization from electrons to <sup>1</sup>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. Mathies, Guinevere Jain, Sheetal K. Griffin, Robert G. 2017-12-04T10:05:20Z Off-resonance NOVEL 2017-12-04T10:05:20Z

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