Fig. 1. Transition of ⁸⁷Rb D² and relevant energy level diagram (a) and sublevel of Zeeman effect splitting (b)

Fig. 2. Distribution of relative atomic absorption

Fig. 3. Experimental facility of cold atoms' density measurement

Fig. 4. Simulation results of coil magnetic field. (a) Relationship between magnetic field variation in Helmholtz coils and total magnetic field; (b) relationship between magnetic field variation in Helmholtz coils and atomic absorption ratio; (c) effect of Helmholtz coil magnetic field on total magnetic field zero position and FWHM of atomic absorption ratio; (d) relationship between total magnetic field gradient and FWHM of the atomic absorption ratio

Fig. 5. Sequence chart of experiment