Large cross-effect dynamic nuclear polarisation enhancements with kilowatt inverting chirped pulses at 94 GHz
Abstract
Dynamic nuclear polarisation (DNP) is a process that transfers electron spin polarisation to nuclei by applying resonant microwave radiation, and has been widely used to improve the sensitivity of nuclear magnetic resonance (NMR). Here we demonstrate new levels of performance for static cross-effect proton DNP using high peak power chirped inversion pulses at 94 GHz to create a strong polarisation gradient across the inhomogeneously broadened line of the mono-radical 4-amino TEMPO. Enhancements of up to 340 are achieved at an average power of a few hundred mW, with fast build-up times (3 s). Experiments are performed using a home-built wideband kW pulsed electron paramagnetic resonance (EPR) spectrometer operating at 94 GHz, integrated with an NMR detection system. Simultaneous DNP and EPR characterisation of other mono-radicals and biradicals, as a function of temperature, leads to additional insights into limiting relaxation mechanisms and give further motivation for the development of wideband pulsed amplifiers for DNP at higher frequencies.
Citation
Zhao , Y , El Mkami , H , Hunter , R I , Casano , G , Ouari , O & Smith , G M 2023 , ' Large cross-effect dynamic nuclear polarisation enhancements with kilowatt inverting chirped pulses at 94 GHz ' , Communications Chemistry , vol. 6 , 171 . https://doi.org/10.1038/s42004-023-00963-w
Publication
Communications Chemistry
Status
Peer reviewed
ISSN
2399-3669Type
Journal article
Description
Funding: This work was supported by UK Research Council EPSRC research grant EP/R13705/1 and Wellcome Trust 099149/Z/12/Z.Collections
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