Collisional ³He and ¹²⁹Xe frequency shifts in Rb--noble-gas mixtures

The Fermi-contact interaction that characterizes collisional spin exchange of a noble gas with an alkali-metal vapor also gives rise to NMR and EPR frequency shifts of the noble-gas nucleus and the alkali-metal atom, respectively. We have measured the enhancement factor $\kappa_{0}$ that characterizes these shifts for Rb-$^{129}$Xe in the high-pressure limit to be 493$\pm$31, making use of the previously measured value of $\kappa_{0}$ for Rb-$^{3}$He. This result allows accurate $^{129}$Xe polarimetry with no need to reference a thermal-equilibrium NMR signal.