Resolving the discrepancy between theoretical and experimental polarization of HP 129Xe using numerical simulations and optical spectroscopy

For emerging biomedical applications of hyperpolarized xenon, the ability to obtain high nuclear spin polarization levels is imperative. Yet, experimental nuclear spin polarization levels of xenon obtained by continuous flow spin-exchange optical pumping are highly variable and often well below theoretical predictions. Identifying possible depolarization mechanisms has been the focus of those trying to rectify this discrepancy. Instead, we revisit assumptions made about the physical system. By using a combination of numerical simulations and in situ optical spectroscopy measurements, we found that lower Rb densities and shorter residence times than typically assumed lead to lower, not higher, theoretical polarization values.