Measurement of Relaxation Rates for NMOR Atomic Magnetometers Based on the Transient Dynamics

Abstract The relaxation rate is a fundamental parameter that characterizes the dynamics of atomic ensembles and plays a critical role in the performance of atomic magnetometers. In this study, a transient dynamics model for the NMOR magnetometer is developed based on multipole moment theory, revealing that the decay rate of the transient response to a step magnetic field from zero to certain value is determined by both transverse and longitudinal relaxation rates, whereas that to a step magnetic field from certain value to zero depends solely on the longitudinal relaxation rate. This distinction enables the independent determination of the two relaxation rates. To validate the proposed method, transverse and longitudinal relaxation rates are experimentally measured under various laser powers, which are consistent with the Lorentzian linewidths extracted from magnetic resonance curve fitting. This study provides valuable insights into atomic transient dynamics and contributes to the fast measurement of relaxation rates in NMOR magnetometers.