Polarization transfer via field sweeping in parahydrogen-enhanced nuclear magnetic resonance

摘要

We show that in a spin system of two magnetically inequivalent protons coupled to a heteronucleus such as C-13, an adiabatic magnetic field sweep, passing through zero field, transfers the 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-C-13]maleic acid, which is prepared via the reaction between [1-C-13] 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 10(4) in the C-13 spectra of [1-C-13]maleic acid in a 1.4 T magnetic field. Published under license by AIP Publishing.