Frequency shifts in noble-gas comagnetometers

Abstract

Polarized nuclei are a powerful tool in nuclear-spin studies and in the search for physics beyond the standard model. Systems which compare two nuclear species have thus far been limited by anomalous yet reproducible frequency variations of unknown origin. We studied the self-interactions in a $^{3}\mathrm{He}\ensuremath{-}^{129}\mathrm{Xe}$ system by independently addressing, controlling, and measuring the influence of each component of the nuclear-spin polarization. Our results directly rule out prior explanations of the shifts and demonstrate experimentally that they can be explained by species-dependent self-interactions. We also report a gas-phase frequency shift induced by $^{129}\mathrm{Xe}$ on $^{3}\mathrm{He}$.