Characterization of Atomic Motion in Alkali Metal Vapor Cells

Alkali metal atomic vapor cells serve as the core sensitive component of Spin-Exchange Relaxation-Free (SERF) magnetometers, primarily including two types, i.e., buffer gas cells and anti-relaxation coated cells. Significant differences of atomic motion behavior existing between two types of cells results in distinctly different polarization distributions and sensor response characteristics. This paper conducts a comprehensive analysis of atomic transient behavior, steady-state polarization distribution, and differential responses to gradient magnetic fields in both cell types. The results indicate that under low-intensity optical pumping condition, anti-relaxation coated cells achieve a relatively uniform polarization distribution, maintain high polarization while effectively mitigating the broadening effects induced by gradient magnetic fields. These findings provide important insights for optimizing the performance of SERF magnetometers and theoretical support for the application of MEMS coated cells.