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High‐field solution state DNP  using cross‐correlations

High‐field solution state DNP  using cross‐correlations
High‐field solution state DNP  using cross‐correlations

At the magnetic fields of common NMR instruments, electron Zeeman frequencies are too high for efficient electron-nuclear dipolar cross-relaxation to occur in solution. The rate of that process fades with the electron Zeeman frequency as ω -2 – in the absence of isotropic hyperfine couplings, liquid state dynamic nuclear polarisation (DNP) in high-field magnets is therefore impractical. However, contact coupling and dipolar cross-relaxation are not the only mechanisms that can move electron magnetisation to nuclei in liquids: multiple cross-correlated (CC) relaxation processes also exist, involving various combinations of interaction tensor anisotropies. The rates of some of those processes have more favourable high-field behaviour than dipolar cross-relaxation, but due to the difficulty of their numerical – and particularly analytical – treatment, they remain largely uncharted. In this communication, we report analytical evaluation of every rotationally driven relaxation process in liquid state for 1e1n and 2e1n spin systems, as well as numerical optimisations of the steady-state DNP with respect to spin Hamiltonian parameters. A previously unreported cross-correlated DNP (CCDNP) mechanism was identified for the 2e1n system, involving multiple relaxation interference effects and inter-electron exchange coupling. Using simulations, we found realistic spin Hamiltonian parameters that yield stronger nuclear polarisation at high magnetic fields than dipolar cross-relaxation.

Cross-correlated relaxation, Dynamic nuclear polarisation, Three-spin effects
1090-7807
Concilio, Maria G
a28efff1-e031-475b-afbc-10129875c879
Soundararajan, Murari
f9f161fb-9779-4085-9bbd-2a699ee5e712
Frydman, Lucio
4f00a1a4-d3a4-47fc-b9c9-50813cb39110
Kuprov, Ilya
bb07f28a-5038-4524-8146-e3fc8344c065
Concilio, Maria G
a28efff1-e031-475b-afbc-10129875c879
Soundararajan, Murari
f9f161fb-9779-4085-9bbd-2a699ee5e712
Frydman, Lucio
4f00a1a4-d3a4-47fc-b9c9-50813cb39110
Kuprov, Ilya
bb07f28a-5038-4524-8146-e3fc8344c065

Concilio, Maria G, Soundararajan, Murari, Frydman, Lucio and Kuprov, Ilya (2021) High‐field solution state DNP  using cross‐correlations. Journal of Magnetic Resonance, 326, [106940]. (doi:10.1016/j.jmr.2021.106940).

Record type: Article

Abstract

At the magnetic fields of common NMR instruments, electron Zeeman frequencies are too high for efficient electron-nuclear dipolar cross-relaxation to occur in solution. The rate of that process fades with the electron Zeeman frequency as ω -2 – in the absence of isotropic hyperfine couplings, liquid state dynamic nuclear polarisation (DNP) in high-field magnets is therefore impractical. However, contact coupling and dipolar cross-relaxation are not the only mechanisms that can move electron magnetisation to nuclei in liquids: multiple cross-correlated (CC) relaxation processes also exist, involving various combinations of interaction tensor anisotropies. The rates of some of those processes have more favourable high-field behaviour than dipolar cross-relaxation, but due to the difficulty of their numerical – and particularly analytical – treatment, they remain largely uncharted. In this communication, we report analytical evaluation of every rotationally driven relaxation process in liquid state for 1e1n and 2e1n spin systems, as well as numerical optimisations of the steady-state DNP with respect to spin Hamiltonian parameters. A previously unreported cross-correlated DNP (CCDNP) mechanism was identified for the 2e1n system, involving multiple relaxation interference effects and inter-electron exchange coupling. Using simulations, we found realistic spin Hamiltonian parameters that yield stronger nuclear polarisation at high magnetic fields than dipolar cross-relaxation.

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Accepted/In Press date: 9 February 2021
Published date: May 2021
Keywords: Cross-correlated relaxation, Dynamic nuclear polarisation, Three-spin effects

Identifiers

Local EPrints ID: 448911
URI: http://eprints.soton.ac.uk/id/eprint/448911
ISSN: 1090-7807
PURE UUID: cc532b0d-e173-4e66-ad66-92e4cba595d2
ORCID for Ilya Kuprov: ORCID iD orcid.org/0000-0003-0430-2682

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Date deposited: 10 May 2021 16:32
Last modified: 17 Mar 2024 06:32

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Contributors

Author: Maria G Concilio
Author: Murari Soundararajan
Author: Lucio Frydman
Author: Ilya Kuprov ORCID iD

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