Accurate Determination of Spin-Exchange Relaxation in a Self-Compensated Atomic Comagnetometer

The spin-exchange (SE) relaxation of the electron spins limits the sensitivity of the self-compensated atomic comagnetometer. In this article, a novel method for measuring the SE relaxation based on the pulse response of the comagnetometer is proposed. The SE relaxation is measured from the difference between the transverse and longitudinal relaxation of the electron spins, which are synchronously extracted from the responses along the probe and pump laser directions to a series of pulsed magnetic fields. Furthermore, we investigate the variation of the SE relaxation with different pump laser power densities and cell temperatures based on this method. The results indicate that there is a maximum of the SE relaxation with the increase of the pump laser power density, and the pump laser power density corresponding to the maximum increases with the cell temperature. The theory and method presented here not only shed light on the way to suppress the SE relaxation in the self-compensated comagnetometer, but also have the potential to be applied to other optically pumped atomic sensors.