Live magnetic observation of parahydrogen hyperpolarization dynamics

Nuclear spin hyperpolarization is used in physics, chemistry, and medicine to produce strong magnetization unachievable by equilibrium polarization techniques. Hyperpolarization enables magnetic resonance spectroscopy and imaging with minute samples, and is used to produce MRI spin-tracers and polarized physics targets. Although widely used, the dynamics of the hyperpolarization process have never been studied `live' due to the extremely low (Hz-band) frequencies involved, and/or detector saturation by the driving fields used. Here, we use an atomic magnetometer with sub-pT sensitivity to observe, in real time, the complex dynamics of hyperpolarization, without disturbing or disrupting the process. We start by examining parahydrogen-induced ^1H and ^13C magnetization build-up during adiabatic eigenbasis transformations in the μT-field avoided state crossings at the heart of the process; we see live hyperpolarization dynamics including coherent oscillations, leakage mechanisms and dipolar shifts that would be challenging or impossible to observe by post hoc measurement. We then extend the methods to observe the chemical-exchange-driven ^13C hyperpolarization of [1-^13C]-pyruvate – the most important spin tracer for clinical metabolic imaging. Beyond the interests of hyperpolarization, the observation of adiabatic transitions in real-time is a fundamentally new approach to NMR, reveals previously hidden nuclear spin dynamics and enables quantum control and live process optimization in a variety of chemical scenarios.