Scanning Nuclear Spin Level Anticrossings by Constant-Adiabaticity Magnetic Field Sweeping of Parahydrogen-Induced 13 C Polarization.

The polarization transfer between 1 H protons and 13 C heteronuclei is of central importance in the development of parahydrogen-based hyperpolarization techniques dedicated to the production of 13 C-hyperpolarized molecular probes. Here we unveil the spin conversion efficiency in the polarization transfer between parahydrogen-derived protons and 13 C nuclei of an ethyl acetate biomolecule, formed by the homogeneous hydrogenation of vinyl acetate with parahydrogen, obtained by applying constant-adiabaticity sweep profiles at ultralow magnetic fields. The experiments employed natural C-13 abundance. Spin level anticrossings can be detected experimentally using a scanning approach and are selected to improve the polarization transfer efficiency. 13 C polarization of up to 12% is readily achieved on the carbonyl center. The results demonstrate the simplicity, reproducibility, and high conversion efficiency of the technique, opening the door for a refined manipulation of hyperpolarized spins in both basic science experiments ( e.g ., state-selected spectroscopy in the strong-coupling regime) and biomedical nuclear magnetic resonance applications.