Simultaneous Determination of the Spin Polarizations of Noble-Gas and Alkali-Metal Atoms Based on the Dynamics of the Spin Ensembles

We demonstrate a method for simultaneously measuring the spin polarizations of noble-gas and alkali-metal atoms. Under a low magnetic field, the polarized alkali-metal and noble-gas spin ensembles exhibit novel dynamics in the self-compensation and resonance regimes, which can be used to measure the polarizations. We perform this method on a $\mathrm{K}$-$\mathrm{Rb}$-${}^{21}$$\mathrm{Ne}$ comagnetometer with various operation temperatures and pump-light intensities. The polarization of alkali-metal electrons from 0.245 to 0.964 and the polarization of noble-gas nuclear spins from 0.01 to 0.065 are measured with relative uncertainties less than $12.4\mathrm{%}$. The measured polarizations are consistent with the theoretical model and are also verified by the traditional polarization-measurement method.