Parahydrogen Induced Polarization of Water and other Neat Liquids by Heterogeneous Catalysis

We have discovered a heterogeneous catalyst for the alignment of proton magnetic moments in water molecules (as well as methanol and ethanol molecules) from parahydrogen, the metastable singlet spin isomer of dihydrogen. After simply bubbling para-enriched H₂ gas through a suspension of the catalyst particles in water, the water protons yield intense stimulated emission NMR signals, corresponding to a negative spin temperature. The phenomenon is dubbed SWAMP (Surface Water Acquires Magnetized Protons from Parahydrogen). Parahydrogen induced polarization (PHIP) of water by heterogeneous catalysis has not been previously reported in the past three decades of PHIP research. Details about the catalyst and the molecular mechanism for the interfacial process, including a density operator model for the spin dynamics, will be presented. SWAMP is a fast and scalable method for producing hyperpolarized pure liquid water, free from polarizing radicals or catalyst residues, which could be transformative to the advancement of MRI and other applications.