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Parahydrogen-enhanced zero-field nuclear magnetic resonance



Svenja A. Knappe, T. Theis, P. Ganssle, G Kervem, M Ledbetter, D Budker, A Pines, John E. Kitching


Nuclear magnetic resonance (NMR) is a powerful analytical tool for determination of molecular structure and function, with broad impact in biology, medicine, materials science, and fundamental research. Conventionally, NMR is performed in multiTesla magnetic fields in order to produce nuclear spin polarization and to maximize detection efficiency of inductive pickup. Despite the use of such large magnetic fields, the nuclear spin-polarization is still quite small, about 1 part in 32,000 for protons in 10 T magnet. Here we demonstrate that NMR can be performed without any magnets by using parahydrogen to produce large nuclear spin polarization, and by using high sensitivity atomic magnetometers to detect this polarization. Sensitivity is sufficient to easily observe 13C-1H J-couplings in natural-abundance compounds. Analysis of J-couplings can be used to obtain important information regarding nuclear spin topology, bond angle and torsion, and hybridization of molecular orbitals. To the best of our knowledge, this represents the first observation of parahydrogen induced polarization at zero magnetic field, highlighting an uncommon mechanism by which the symmetry of the singlet state of parahydrogen can be broken in the absence of chemical shifts. This technique may be applied to mobile, low-filed NMR spectroscopy, imaging, and studies of catalytic processes on chip-scale devices.
Nature Physics


nuclear magnetic resonance, atomic magnetometer, low-field NMR, parahydrogen
Created May 1, 2011, Updated February 19, 2017