Fig. 1. Schematic of the experimental apparatus

Fig. 2. Energy level splitting diagram of the ground state and first excited state of atom ⁸⁷Rb and its selective transitions in the pumping process. (a) Energy level splitting; (b)selective transitions

Fig. 3. Timing and FID signal in a single sampling period. (a) Signal of a single sampling period and the corresponding timing of pumping light and RF pulse; (b) one signal fitting result

Fig. 4. Atomic magnetic resonance spectra at different pump powersintensities at different temperatures with the magnetic field of 1000 nT. (a) 90 ℃; (b) 100 ℃; (c) 110 ℃; (d) 120 ℃

Fig. 5. Relationship between the resonance linewidths (the amplitudes) of FID signals and the pump laser

Fig. 6. Relationship between the resonance linewidths and the amplitudes of FID signals at different temperatures with the magnetic field of 1000 nT. (a) 90 ℃; (b) 100 ℃; (c) 110 ℃; (d) 120 ℃

Fig. 7. Relationship between the resonance linewidth and the magnetic field