104. Polarization Transfer via Field Sweeping in Parahydrogen-Enhanced Nuclear Magnetic Resonance

James Eills, John W. Blanchard, Teng Wu, Christian Bengs, Julia Hollenbach, Dmitry Budker, Malcolm H. Levitt, JCP, (2019) DOI: 10.26434/chemrxiv.7946807

We show that in a spin system of two magnetically inequivalent protons coupled to a heteronucleus such as 13C, an adiabatic magnetic field sweep, passing through zero field, transfers proton singlet order into magnetization of the coupled heteronucleus. This effect is potentially useful in parahydrogen-enhanced nuclear magnetic resonance, and is demonstrated on singlet-hyperpolarized [1-13C]maleic acid, which is prepared via the reaction between [1-13C]acetylene dicarboxylic acid and para-enriched hydrogen gas. The magnetic field sweeps are of microtesla amplitudes, and have durations on the order of seconds. We show a polarization enhancement by a factor of 104 in the 13C spectra of [1-13C]maleic acid in a 1.4 T magnetic field.