Comparison and analysis of methods for measuring the spin transverse relaxation time of rubidium atomic vapor

The spin transverse relaxation time (T_2) of atoms is an important indicator for precision measurement. Several methods have been proposed to characterize the T_2 of atoms. In this paper, the T_2 of rubidium (Rb) atomic vapor in the same cell was measured using four measuring methods, namely spin noise spectrum signal fitting, improved free induction decay (FID) signal fitting, w_m-broadening fitting, and magnetic resonance broadening fitting. Meanwhile, the T_2 of five different types of Rb atomic vapor cells were measured and characterized. A comparative analysis visualizes the characteristics of the different measuring methods and the effects of buffer gas on T_2 of Rb. We theoretically and experimentally analyzed the applicability of the different methods, and then demonstrated that the improved FID signal fitting method provides the most accurate measurement because of the clean environment in which the measurements were taken. Furthermore, we demonstrated and qualitatively analyzed the relationship between the atomic number density and the T_2 of Rb. This work provides analytical insight in selecting atomic vapor cells, and may shed light on the improvement of the sensitivity of atomic magnetometers.