Sr原子自电离态的电场效应

用多步激发的方法,将Sr原子从基态5s~2经价态4α~(-2)激发至(4d_(3/2)np,n_f)J=1和(4d_(5/2)np,nf)J=1自电离系列,观察其在外电场0～5kV/cm内的光谱.对所观察到的n=12,13,14附近的斯塔克谱图进行了分析与讨论.     

利用光电离技术研究奇宇称的Sm原子光谱

采用一台频率可扫描的染料激光器将Sm原子从4f66s2 7FJ(J=1,2)态分别激发到具有不同电子组态的若干原子态上,然后利用光电离技术对处于上述状态的Sm原子进行高灵敏探测.通过波长固定在355nm的紫外激光器,我们对一系列具有4f66s6p或者4f55d6s2电子组态的原子状态进行了精密的光谱测量.本实验研究不但确定了这些态的能级位置,还给出了它们的相对光谱强度.通过理论方法对光谱数据详细的分析,我们不但确认了文献中Sm原子的部分奇字称能级的位置和光谱标识,还同时给出了许多新的跃迁及其光谱特性.     

拉曼型光致离化系统中的暗态效应

利用Ｗｉｎｇｅｒ－Ｗｅｉｓｓｋｏｐｆ近似研究了光致离化系统中的暗态效应，在双模量子化光场的驱动下，三个束缚态形成一个暗态，即使在ｔ→∞的条件下，原子在该暗态上也能保持一定的居数，还给出了光子数对原子在束缚态年的占居数的影响。     

用光电离技术探测钐原子的奇宇称束缚激发态的光谱

采用光电离探测方法,对钐原子奇宇称束缚激发态进行了系统研究.通过设计三条不同的激发路径, 采用共振激发方式,先将钐原子分三步从基态激发到不同的束缚激发态,然后采用光电离手段对其进行探测. 通过对第三步激发光的波长进行大范围的扫描,在同一能域内获得了三组不同的光谱. 通过比对三条路径所得到的三组光谱,不仅精确确定了大量奇宇称束缚激发态的能级位置, 而且还获得了相应跃迁的相对强度的信息.最后,通过运用三条不同的激发路径的选择定则, 还确定了上述能级的总角动量. 关键词： 钐原子 束缚激发态 奇宇称 光电离探测     

Experimental study of bound and autoionizing Rydberg states of the europium atom

An isolated-core-excitation (ICE) scheme and stepwise excitation are employed to study the highly excited states of the europium atom. The bound europium spectrum with odd parity in a region of 42400--43500~cm^{ - 1} is measured, from which spectral information on 38 transitions, such as level position and relative intensity, can be deduced. Combined with information about excitation calibration and the error estimation process, the selection rules enable us to determine the possible values of total angular momentum J for the observed states. The autoionization spectra of atomic europium, belonging to the 4f^{7}6p{nl} (l=0, 2) configurations, are systematically investigated by using the three-step laser resonance ionization spectroscopy (RIS) approach. With the ICE scheme, all the experimental spectra of the autoionizing states have nearly symmetric profiles whose peak positions and widths can be easily obtained. A comparison between our results and those from the relevant literature shows that our work not only confirms many reported states, but also discovers 14 bound states and 16 autoionizing states.     

Multistep excitation of autoionizing states of the samarium atom

In this work, 4f ⁶6pnl and 4f ⁵5d6snl (l=0,2) autoionizing states of the samarium (Sm) atom, especially those with lower principal quantum number, have been studied, using the isolated-core excitation scheme with three dye lasers. In the energy region between 57 990 and 61 030 cm⁻¹, there are 74 autoionizing states of the Sm atom observed. These states can be classified into the autoionization series converging to four different ionization limits. In most cases, the line shapes of these autoionizing states are nearly symmetric, from which the level energies and widths can be easily obtained by fitting the experimental spectra to the Lorentzian profiles. In addition, several spectroscopic properties of these autoionizing states, such as configuration interaction, are also discussed.     

非简并Λ型三能级原子的速度选择相干布居俘获

研究了非简并Λ型三能级原子速度选择相干布居俘获与原子能级结构的非对称性以及原子-激光失谐之间的关系.指出相对于简并、共振情况，原子动量分布的概率峰峰值降低、最可几动量发生变化，而且原子的俘获时间也变得很长.     

Ba原子6pns自电离光谱的研究

本文采用三台染料激光器分步激发Ba原子,利用自电离过程产生离子或电子.当固定第一和第三步激光波长而扫描第二步激光波长时,便可获得Ba原子6sns Rydberg态的光谱.当固定第一和第二步激光波长而扫描第三束激光波长时,便可获得Ba原子6pns自电离态的光谱.运用多通道量子亏损理论对实验光谱进行了分析,着重针对主量子数n≤10的6pns自电离态的光谱检验了所用理论模型的准确性,取得了满意的结果.     

The nonclassical properties of the superposition involving two squeezing coherent states

ＴｈｅｎｏｎｃｌａｓｓｉｃａｌｐｒｏｐｅｒｔｉｅｓｏｆｔｈｅｓｕｐｅｒｐｏｓｉｔｉｏｎｉｎｖｏｌｖｉｎｇｔｗｏｓｑｕｅｅｚｉｎｇｃｏｈｅｒｅｎｔｓｔａｔｅｓＺＯＵＡｎｈｕａ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓ，ＳｈｅｎｇｒａｏＴｅａｃｂｏｒｓ＇Ｃ...     

Photoionization spectra of even-parity states of Sm atom with multistep excitation

Two-color stepwise excitation and photoionization schemes are adopted to study the spectra of bound even-parity high-lying states of the Sm atom with three different excitation paths via the 4f⁶6s6p ⁷D_J (J=1, 2 and 3) intermediate states. In order to obtain the information of these high-lying states, the Sm atom in these high-lying states is photoionized with an extra photon. Among 231 states detected in the energy region between 35,545 and 44,225 cm⁻¹, 108 states are newly discovered, while the rest can be identified as the same with the literature. In most cases, comparisons of the spectra corresponding to the three different excitation paths may partially determine the total angular momentum of the observed peaks with the selection rules. In addition, the relative intensities of all related transition lines are given.     

Studies on odd-parity states of the Sm atom

Two-step excitation and ionization processes are used to detect Sm atoms in many excited states populated with tunable lasers. The wavelength of the first laser is tuned to the resonances from the Sm 4f^6 6s^2 ^7FJ （J=0 6） states to many odd-parity states with different electronic configurations, where the atoms are detected by photoionization process using an ultraviolet laser with a wavelength of 355 nm. Precise measurements on the energy level and intensity for many Sm 4f^6 6s6p and 4f^5 5d6s^2 states have been carried out. In a theoretical analysis on the spectral data, such as peak position, relative intensity, many transitions can be identified as the resonances from the Sm 4f^6 6s^2 7FJ （J=0-6） states to the atomic states with 4f^6 6s6p and 4f^5 5d6s^2 electronic configurations. This work also reports many spectral data on the odd-parity states that cannot be found in the literature.     

Generation of entangled coherent states for two cavity modes via resonant interaction with a V-type three-level atom

This paper proposes a scheme for the generation of entangled coherent states for two cavity modes. In the scheme a V-type three-level atom is sent through a two-mode cavity filled with a coherent field. After the atom cavity interaction and detection of the atomic state the cavity modes may evolve to a superposition of two-mode coherent states. As the scheme is based on resonant atom-cavity interaction, the required interaction time is short, which is important in view of the decoherence. Moreover, additional classical pulses are unnecessary before and after the atom-cavlty interaction.     

Eu原子4f~76p_(3/2)6d自电离过程的动力学特性

采用孤立实激发技术(isolated-core excitation, ICE)及速度影像技术(velocity-map imaging,VMI),研究了Eu原子4f~76p_(3/2)6d自电离过程的动力学特性.孤立实激发技术用于将Eu原子从基态4f~76s~(2 8)S_(7/2)经中间态4f~76s6p激发到4f~76s6d里德堡态,然后将其进一步激发至4f~76p_(3/2)6d自电离态;速度影像技术用于探测其自电离过程的动力学特性,从而获得自电离衰变的分支比(branch ratio, BR)和弹射电子的角分布(angular distribution, AD).自电离衰变的分支比代表离子的能量分布,从中获得VMI影像的径向信息;而通过各向异性参数描述的弹射电子的角分布揭示了VMI影像的角向信息.此外,讨论了自电离衰变分支比和弹射电子角分布在整个自电离共振能域内的变化情况.基于4f~76s~+和4f~75d~+两个离子态的分支比,讨论了实现Eu离子粒子数反转的可能性.     

Photoionization microscopy of hydrogen atom near a metal surface

We have studied the ionization of Rydberg hydrogen atom near a metal surface with a semiclassical analysis of photoionization microscopy. Interference patterns of the electron radial distribution are calculated at different scaled energies above the classical saddle point and at various atom-surface distances. We find that different types of trajectories contribute predominantly to different manifolds in a certain interference pattern. As the scaled energy increases, the structure of the interference pattern evolves smoothly and more types of trajectories emerge. As the atom approaches the metal surface closer, there are more types of trajectories contributing to the interference pattern as well. When the Rydberg atom comes very close to the metal surface or the scaled energy approaches the zero field ionization energy, the potential induced by the metal surface will make atomic system chaotic. The results also show that atoms near a metal surface exhibit similar properties like the atoms in the parallel electric and magnetic fields.     

Photoionization microscopy of Rydberg hydrogen atom in a non-uniform electrical field

In this paper,we investigate the photoionization microscopy of the Rydberg hydrogen atom in a gradient electric field for the first time.The observed oscillatory patterns in the photoionization microscopy are explained within the framework of the semiclassical theory,which can be considered as a manifestation of interference between various electron trajectories arriving at a given point on the detector plane.In contrast with the photoionization microscopy in the uniform electric field,the trajectories of the ionized electron in the gradient electric field will become chaotic.An infinite set of different electron trajectories can arrive at a given point on the detector plane,which makes the interference pattern of the electron probability density distribution extremely complicated.Our calculation results suggest that the oscillatory pattern in the electron probability density distribution depends sensitively on the electric field gradient,the scaled energy and the position of the detector plane.Through our research,we predict that the interference pattern in the electron probability density distribution can be observed in an actual photoionization microscopy experiment once the external electric field strength and the position of the electron detector plane are reasonable.This study provides some references for the future experimental research on the photoionization microscopy of the Rydberg atom in the non-uniform external fields.     

Photoionization microscopy of Rydberg hydrogen atom near a dielectric surface

Based on the semiclassical analysis of photoionization microscopy, we study the ionization of the Rydberg hydrogen atom near a dielectric surface. The radial electron probability density distributions on a given detector plane are calculated at different scaled energies and near different dielectric surfaces. We find due to the interference effect of different types of electron trajectories arriving at a given point on the detector plane, oscillatory structures appear in the electron probability density distributions. With the increase in the scaled energy, more types of electron ionization trajectories appear and the oscillatory structure in the electron probability density distributions becomes complex. Besides, the dielectric constant of the dielectric surface can also affect the electron probability density distributions. Since the photoionization microscopy interference pattern recorded on the detector plane reflects the distribution of the square modulus of the transverse component of the electronic wave function, with the recorded interference pattern, we can investigate the ionization dynamics of the Rydberg atom near surfaces clearly. This study provides some reference values for the future experiment research on the photoionization microscopy of the Rydberg atom near dielectric surfaces.     

Autoionization spectra of Sm atom

Spectra of autoionizing states of the Sm atom in an energy region between 45948.9 cm-1 and 46943.6 cm-1 are systematically investigated by a three-color multi-step resonant excitation scheme with three different excitation paths.The three intermediate states,4f 66s7s 7F3,4f 66s7s 7F4,and 4f 66s7s 9F5 are employed for the three paths,respectively.Based on precise calibration of wavelength,the level energies of 112 autoionizing states are determined with the line widths and the relative line intensities of the related transitions.The possible influence of configuration interaction on the line shape of autoionizing state is also discussed.In addition,a unique value of J,the total angular momentum,is assigned to all detected states by comparing the three spectra obtained with the different excitation paths.     

钙原子的双电子激发自电离光谱

用三步激发方法,通过3d~2~3P_0价态得到了3dnp和3dnf,J=1系列的70多个双电子激发自电离能级,并讨论了这些光谱线的归属.     

Ba原子6pnd(J=1, 3)自电离光谱的实验研究

采用三台可调谐激光实施孤立实激发,分三步将处于基态的Ba原子激发到6p_1/2nd(J=1,3)和6p_3/2nd(J=1,3)自电离态上,获得了分别从6snd¹D₂(n=7—15)和6snd³D₂(n=7—12) 激发而得到的6p_1/2nd(J=1,3)和6p_3/2nd (J=1,3)自电离光谱,重点对主量子数n较低的自电离态进行了实验研究. 通过光谱的线形拟合得到了上述能级的位置和宽度等数据,进而获得了量子亏损和约化宽度等信息. 通过对不同系列的自电离光谱的分析和比较,详细讨论了这些自电离态的光谱特征及其复杂光谱结构的成因. 关键词： 孤立实激发 组态相互作用 自电离态     

The Wigner function and phase properties of superposition of two coherent states with the vacuum state

This paper discusses some statistical properties of the superposition of two coherent states with a vacuum state, such as sub-Poissonian photon statistics and negativity of the Wigner function. Phase probability distribution and phase variance are calculated. Special cases of the constructed superposition states are presented. The results show that depending on the vacuum state coefficient γ and the coherent state coefficient α, it can generate a variety of nonclassical states.