Publications

Hyperpolarized nuclear spins in molecules exhibit high magnetization that is unachievable by classical polarization techniques, making them widely used as sensors in physics, chemistry, and medicine. The state of a hyperpolarized material, however, is typically only studied indirectly and with partial destruction of magnetization, due to the nature of conventional detection by resonant-pickup NMR spectroscopy or imaging. Here, we establish atomic magnetometers with sub-pT sensitivity as an alternative modality to detect in real time the complex dynamics of hyperpolarized materials without disturbing or interrupting the magnetogenesis process. As an example of dynamics that are impossible to detect in real time by conventional means, we examine parahydrogen-induced H-1 and C-13 magnetization during adiabatic eigenbasis transformations at mu mu T-field avoided crossings. Continuous but nondestructive magnetometry reveals previously unseen spin dynamics, fidelity limits, and magnetization backaction effects. As a second example, we apply magnetometry to observe the chemical-exchange-driven C-13 hyperpolarization of [1-C-13]-pyruvate-the most important spin tracer for clinical metabolic imaging. The approach can be readily combined with other high-sensitivity magnetometers and is applicable to a broader range of general observation scenarios involving production, transport, and systems interaction of hyperpolarized compounds.

JTD Keywords: Adiabaticity, Dnp, Field, Hyperpolarization, Nmr, Nuclear spins, Optical magnetometry, Order, Para-hydrogen, Parahydrogen, Polarimetry, Polarization transfer

Photochemically induced dynamic nuclear polarization (photo-CIDNP) enables nuclear spin ordering by irradiating samples with light. Polarized spins are conventionally detected via high-field chemical-shift-resolved NMR (above 0.1 T). In this Letter, we demonstrate in situ low-field photo-CIDNP measurements using a magnetically shielded fast-field-cycling NMR setup detecting Larmor precession via atomic magnetometers. For solutions comprising mM concentrations of the photochemically polarized molecules, hyperpolarized 1H magnetization is detected by pulse-acquired NMR spectroscopy. The observed NMR line widths are about 5 times narrower than normally anticipated in high-field NMR and are systematically affected by light irradiation during the acquisition period, reflecting a reduction of the transverse relaxation time constant, T2*, on the order of 10%. Magnetometer-detected photo-CIDNP spectroscopy enables straightforward observation of spin-chemistry processes in the ambient field range from a few nT to tens of mT. Potential applications of this measuring modality are discussed.

JTD Keywords: field-dependence, mechanism, nmr, parahydrogen, photo-cidnp, polarization, quinone, spin-hyperpolarization, Radical-pair