Field-cycling NMR experiments in an ultra-wide magnetic field range: relaxation and coherent polarization transfer

• Published in: Physical chemistry chemical physics : PCCP Vol. 20; no. 18; pp. 12396 - 12405
• Main Authors: Zhukov, Ivan V, Kiryutin, Alexey S, Yurkovskaya, Alexandra V, Grishin, Yuri A, Vieth, Hans-Martin, Ivanov, Konstantin L
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 2018
• Subjects: Carbon; Cycles; Experiments; Magnetic fields; Magnetic induction; NMR; Nuclear magnetic resonance; Overhauser effect; Polarization; Polarization (spin alignment)
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c7cp08529j

An experimental method is described allowing fast field-cycling Nuclear Magnetic Resonance (NMR) experiments over a wide range of magnetic fields from 5 nT to 10 T. The method makes use of a hybrid technique: the high field range is covered by positioning the sample in the inhomogeneous stray field of the NMR spectrometer magnet. For fields below 2 mT a magnetic shield is mounted on top of the spectrometer; inside the shield the magnetic field is controlled by a specially designed coil system. This combination allows us to measure T1-relaxation times and nuclear Overhauser effect parameters over the full range in a routine way. For coupled proton-carbon spin systems relaxation with a common T1 is found at low fields, where the spins are "strongly coupled". In some cases, experiments at ultralow fields provide access to heteronuclear long-lived spin states. Efficient coherent polarization transfer is seen for proton-carbon spin systems at ultralow fields as follows from the observation of quantum oscillations in the polarization evolution. Applications to analysis and the manipulation of heteronuclear spin systems are discussed.