研究了里德伯原子系统采用直接解调法对微波调幅信号进行解调时的工作点与基带信号非线性失真之间的关系。首先，利用里德伯原子的电极化率理论表达式，得到在耦合光、探测光和微波的频率均为零失谐条件下，里德伯原子系统对微波调幅信号的解调模型；然后，计算探测光透射率对微波拉比频率的一阶导数和二阶导数，并利用二阶导数为0这一条件，得到里德伯原子汽室的非线性失真最小的点，即最佳线性工作点；最后，采用总谐波失真（THD）来分别研究里德伯原子汽室的静态工作点、基带信号的幅度与解调所引起的非线性失真之间的关系。仿真结果表明，对于里德伯原子¹³³Cs（采用能级6S_1/2、6P_3/2、47D_5/2、48P_3/2），当耦合光拉比频率为2π×2.7 MHz，并且调幅微波基带信号的电场强度幅值为1 mV/m时，工作在最佳线性工作点附近的原子汽室所引入的THD可低至-95.4984 dB。

本文通过测量铯原子的电磁感应透明光谱在微波电场作用下的Autler-Townes分裂间隔,获得了铯蒸气池中高分辨率的毫米波微波电场强度空间分布特征。文中使用32.65 GHz的微波场共振耦合铯里德堡原子49S1／2态和邻近的49P1／2态,得到铯原子6S1／2-6P3／2-49S1／2阶梯型三能级电磁诱导透明光谱分裂信号。我们测量了射频信号发生器输出功率PMW与Autler-Townes分裂宽度的关系,实验结果表明分裂宽度与电场强度(∝PMW)有良好的线性关系。根据此线性关系我们对铯蒸气池一维方向的电场强度空间分布进行了测量,理论上获得的空间分辨率达到λMW／90。

The 4f7 6s(9S)np 8PJ (J=5/2, 7/2, 9/2) Rydberg series converging to the first ionization limit 4f7 6s 9S4 of the Eu atom using the three-step laser excitation and electric-field-ionization (EFI) method are studied. First, the Eu atom is excited from the 4f7 6s2 8So7/2 ground state to the 4f76s7s 8So7/2 state through the 4f7 6s6p 10P9/2 state by the first two dye lasers. Next, it is populated to many higher-n members of the 4f7 6s(9S)np 8PJ Rydberg series by the third dye laser whose wavelength is scanned within a certain range. Finally, the atom in these higher-n states is ionized by the external pulsed electric field. With the field strength up to 2 kV/cm, we can detect the atom in 4f76s(9S)np 8PJ states with n>40. With the given laser line width, the level energies of Rydberg states with n as high as 72 can be determined. We not only confirm the previous data on the 4f76s(9S) np 8PJ Rydberg series, but also extend the n-value assignment significantly by detecting more states.

We present high resolution photoelectron energy spectra from multiphoton ionization (MPI) of Ar subject to laser pulses with wavelength of 400 nm, pulse duration of 35 fs, and maximum intensity of 5×10¹³ W/cm². Ionizations into Ar^{+ 2}P_3/2 and ²P_1/2 channels are observed and distinct resonance structures are found in both ionization channels. The intensity dependence of the resonance structures is explained in terms of the mechanism of Freeman resonance, i.e., transient resonances of alternating current (AC) Stark-shifted Rydberg states at specific intensities within the laser pulse.

The energy levels and lifetimes of 3pns 3P0(n=7-35) and 3pnd 3P0 (n=6-17) series of neutral silicon are calculated and predicted by means of multichannel quantum defect theory (MQDT). In addition, the perturbation caused by core-excited state 3s3p3 is discussed. The 3pnd 3P0 series, especially 3p4d 3P0, 3p5d 3P0, and 3p6d 3P0 are perturbed strongly by the core-excited state 3s3p3 3P0. These cause the lifetime of 3pnd 3P0 (n=5-7) to be less than that of 3p4d 3P0. The lifetimes of 3p14d 3P0 (65479.14 cm-1) and 3p16d 3P0 (65608.77 cm-1) are less than that of their frontal states respectively, because these states are perturbed by 3p22s 3P0 (65476.48 cm-1) and 3p30s 3P0 (65608.99 cm-1) respectively.

Considering the perturbation, the results of theoretical calculation of five Rydberg series energy levels 6s2ns2S1/2(n=7-20),6s2nd2D3/2(n6-20),6s2nd2D5/2(n=6-20),6s2np2P^(0)_(1/2)(n=7-20), and 6s2np2P^(0)_(3/2)(n7-20) for Tl I are presented using the weakest bound electron potential model (WBEPM) theory. Furthermore, the radiative lifetimes of this five series are also calculated. The calculated values of energy levels and lifetimes are in good agreement with the experimental results.

Martin expression about the quantum defect of single-valence atoms is extended to many-valence atoms by identifying the weakest bound electron (WBE) under the weakest bound electron potential model (WBEPM) theory. Six Rydberg series energy levels of 2p6np2Po_(1/2) (n>3), 2p6np2Po_(3/2) (n>3), 2p6nd2D_(3/2) (n>3), 2p6nd2D_(5/2) (n>3), 2p6nf2Fo_(5/2) (n>4), and 2p6nf2Fo_(7/2) (n>4) for Ni XVIII are calculated by this method. The calculated results are in good agreement with the experimental results.