Probing frequency shifts in a dual-isotope Rb-Xe vapor cell using selective resonant RF-field suppression.

We investigate the spin interaction mechanisms in a Rb-Xe vapor cell containing both 129Xe and 131Xe. The Xe polarization is quantitatively related to the Rb polarization through the Fermi-contact interaction between Rb Xe. By selectively suppressing the Xe polarization using a strong resonant radio-frequency (RF) field, it is demonstrated that the RF field itself does not induce measurable shifts in the Xe resonance frequency. Furthermore, measurements of the longitudinal relaxation times show that cross relaxation between the two Xe isotopes is negligible under the present experimental conditions. The remaining frequency shifts, observed at the milliHertz level, are consistent with a mean-field interaction arising from the macroscopic magnetization of polarized Xe nuclei. These results provide a clear understanding of spin interactions in multi-isotope Xe vapor cells and are relevant for high-precision NMR measurements and NMR-based gyroscopes.