Fig. 1. (a) The V-type cesium three-level system; a 318.6 nm ultraviolet laser excited partial cesium atoms from 6S_1/2 (F = 4) ground state to nP_3/2 (n = 70–94) Rydberg state, where is the frequency detuning of pump laser; a 852.3 nm probe laser is locked to 6S_1/2 (F = 4) –6P_3/2 (F' = 5) hyperfine transition. (b) Schematic diagram of experimental setup. OI, optical isolator; EOM, fiber-pigtailed integration optical waveguide phase-type electro-optic modulator; PBS, polarization beam spliter cube; BS, beam spliter plate; DM, dichroic mirror; DPD, differential photo-diode; Ω, the radio-frequency modulated signal applied on EOM (a) 铯原子V型三能级系统, 318.6 nm紫外光将原子从6S_1/2 (F = 4)基态激发到nP_3/2 (n = 70—94)里德伯态, 为激发光相对跃迁频率的失谐量; 852.3 nm探测光频率锁定在6S_1/2 (F = 4)—6P_3/2 (F' = 5)超精细跃迁; (b)实验装置示意图; OI, 光隔离器; EOM, 带输入和输出尾纤的集成光波导型电光位相调制器; PBS, 偏振分束棱镜; BS, 分束片; DM, 双色片; DPD, 差分探测器; , EOM所加的射频调制信号

Fig. 2. Velocity-selective spectra. The frequency of 852.3 nm probe beam is locked on the 6S_1/2 (F = 4)—6P_3/2 (F' = 5) transition and the light power is 159 ; the 318.6 nm coupling beam is scanned over the transition of 6S_1/2 (F = 4)—71P_3/2 and the light power is 1.6 W. Two transmission peaks appeared when the frequency of the coupling beam resonated with the 6S_1/2 (F = 4)—71P_3/2 transition line or blue detuning of 671 MHz, corresponding to atoms which have velocity of v_z = 0 (corresponding to the carrier of 852.3 nm probe beam) and v_z = 213.94 m/s (corresponding to the +1 order 251 MHz radio-frequency modulation component of 852.3 nm probe beam) are excited to 71P_3/2 Rydberg state, respectively. 速度选择单光子跃迁铯原子71P_3/2里德伯态的激发光谱. 852.3 nm探测光共振于6S_1/2 (F = 4)—6P_3/2 (F' = 5)跃迁线, 探测光功率为159 ; 318.6 nm紫外激发光频率在6S_1/2 (F = 4)—71P_3/2态跃迁扫描, 功率为1.6 W; 激发光频率相对71P_3/2态零失谐和蓝失谐671 MHz时, 出现两个透射信号, 分别对应速度组分为v_z=0 (对应852.3 nm探测光的载频)和v_z=213.94 m/s (对应852.3 nm探测光的 + 1级251 MHz射频调制边带)的铯原子被激发到71P_3/2态

Fig. 3. The theory values of quantum defects for cesium nP_3/2 (n = 50–100) Rydberg states. Quantum defect is decreasing with increasing of the principal quantum number n. 铯原子nP_3/2 (n = 50—100)里德伯态量子亏损随主量子数n的变化. 量子亏损随着主量子数n增加而缓慢减小

Fig. 4. Comparison of direct experimentally measured data with calculated values of quantum defects for cesium nP_3/2 (n = 70—94) Rydberg states. The red dots are calculated values and the black cubes are direct experimentally measured data. When the principal quantum number n increasing, the calculated values are almost constant, but the direct experimentally measured data are increasing obviously. This variation trend indicate that some influence factors should be took into account to correct the direct experimentally measured data. 铯原子nP_3/2 (n = 70—94)态的量子亏损计算值与实验直接测量值的对比. 其中红色圆点为计算值, 黑色方块为实验直接测量值; 随着主量子数n的增加, 计算值近乎不变, 而实验直接测量值却是增加的. 这一趋势表明有一些影响因素必须要考虑, 去修正直接实验测量得到的铯原子nP_3/2 (n = 70—94)里德伯态的量子亏损值

Fig. 5. (a) Using the estimated residual DC electric field to correct the direct experimentally measured data, according to the relationship between Stark shift and effective principal quantum number n^*, the magnitude of the residual DC electric field acting on the cesium atomic vapor cell is ~(31 ± 2) mV/cm; (b) after correction of the impact of Stark effect and the measurement error of wavemeter, the corrected experimentally measured quantum defect value of cesium nP_3/2 (n = 70—94) states is ~(3.5591 ±0.0007). This corrected result is consistent with the theoretically calculated value. (a) 利用估算的残余直流电场对量子亏损直接实验测量值进行修正, 根据Stark频移量和有效主量子数n^*的关系, 拟合得到了作用于铯原子气室中的残余直流电场约为 (31 ± 2) mV/cm; (b) 修正Stark效应及波长计测量误差的影响后, 铯原子nP_3/2(n = 70—94)态量子亏损的实验测量修正值约3.5591 ± 0.0007; 实验数据与计算值相吻合