Fig. 1: Schematic view of PHIP-X, magnetic field cycling (MFC,) and RF pulse sequences used in simulations and experiments.
From: Nuclear spin polarization of lactic acid via exchange of parahydrogen-polarized protons
We consider 4 essential steps of PHIP-X (a): hydrogenation (A), the polarization of the exchanging protons (B), transfer of the exchanging protons (C), and polarization of the target nucleus (D). In our experiment, the sample was exposed to three main fields (b): BPol0 during hydrogenation (≈5 s), BPol1 during sample transfer (1.5 s), and B0 during excitation and detection. Note that a finite transition took place in between the fields (≈a few 100 ms). At high field40, a pulse sequence (c) was applied to polarize 13C, either with timings adjusted to the 139–145 Hz couplings of the firmly bound 1H-13C (SOT 1), or to the 3 Hz interaction between the labile proton and 13C (SOT 2). Here, we used 13C-methanol and 13C3-lactic acid as target molecules.
