中文摘要：

在室温下的原子气室中,基于铯原子6S_（1/2）—6P_（3/2）—7S_（1/2）（852.3 nm＋1469.9 nm）阶梯型能级系统,利用电光调制器的主频和±1级边带分别产生的三套双共振吸收光谱,当驱动电光调制器的信号源频率严格等于7S_（1/2）态超精细分裂的能级间隔时,三套谱线中的一些超精细跃迁谱线重叠且线宽最窄,利用这一现象很好地避免了激光器频率扫描时非线性效应的影响,测量出了7S_（1/2）态超精细分裂能级间隔：2183.72 MHz±0.23 MHz,并计算出该态的磁偶极超精细常数：A_（hfs）=545.93 MHz±0.06 MHz,与文献中报道的测量结果一致.

英文摘要：

Hyperfine-structure（HFS） of atoms results from the interactions between the nuclear magnetic dipole moment and the magnetic field generated by the electrons（related to the magnetic dipole hyperfine constant Ahfs）, and between the nuclear electric quadrupole moment and the electric field gradient due to the distribution of charge within atoms（related to the electric quadrupole hyperfine constant Bhfs）, so the accurate measurement of HFS is of interest in many fields,including atomic parity nonconservation, tests of fundamental physics, electron-nucleus interaction, and high resolution spectrum and so on. Generally, in order to obtain the atomic spectra, the frequency of laser needs to be scanned over the hyperfine transitions of atoms, so the nonlinear effect from the laser frequency scanning often limits the measurement accuracy of hyperfine splitting. In this paper, we solve this problem, and demonstrate a novel method to measure the hyperfine splitting of atoms. Taking cesium（Cs） for example, based on the Cs 6S_（1/2）–6P_（3/2）–7S_（1/2）（852.3 nm ＋1469.9 nm） ladder-type atomic system, three sets of optical-optical double resonance（OODR） spectra are obtained in a room-temperature vapor cell, when the 852.3 nm laser is tuned to the 6S_（1/2）（F = 4）–6P_（3/2）（F′= 4） resonant transition,and the carriers of 1469.9 nm probe laser accompanied with ±1 sidebands from a phase-type electro-optical modulator（EOM） are scanned over the whole 6P_（3/2）–7S_（1/2）hyperfine transitions. Owing to the Doppler effect, some of the hyperfine transitions in these three sets of OODR spectra overlap with the narrowest linewidth only when the frequency of the signal driving EOM equals the value of hyperfine splitting 7S_（1/2）state. Using this phenomenon which can effectively avoid the nonlinear influence on the measurement during the frequency scanning process of 1469.9 nm laser, we measure the hyperfine splitting of 7S_（1/2）state to be（2183.72±0.23） MHz,