Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets

The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters $E_r}$ and $\Ga/2$ of a hydrogen atom in parallel electric and magnetic fields. The method can calculate the ground and higher excited resonances accurately and efficiently. The resonance parameters with accuracies of $10^{-9}-10^{-12}$ for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones. Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.     

Resonances of a hydrogen atom in strong parallel electric and magnetic fields using B-spline basis sets

The B-spline basis set plus complex scaling method is applied to the numerical calculation of the exact resonance parameters Er and Г/2 of a hydrogen atom in parallel electric and magnetic fields. The method can calculate the ground and higher excited resonances accurately and efficiently. The resonance parameters with accuracies of 10^-9 - 10^-12 for hydrogen atom in parallel fields with different field strengths and symmetries are presented and compared with previous ones. Extension to the calculation of Rydberg atom in crossed electric and magnetic fields and of atomic double excited states in external electric fields is discussed.     

Na原子斯塔克态寿命的实验测定

在１２５０￣２０００Ｖ／ｃｍ的静电场变化范围内，用可调谐激发实现Ｎａ原子在ｎ＝１７，ｍ＝０斯塔克族各能态布局，采用延迟脉冲场电离方法测量了各斯塔克能态在不同外电场下的寿命，讨论了外电场强度和环境黑体辐射对斯塔克态寿命的影响。     

Novel Experimental Method in the Study of Double Rydberg States by Laser Resonance Excitation

1.IntroductionSequentia1multisteplaserexcitationhasbeenextensivelyusedtostudydoublyexcit-edstatesofa1ka1ine-earthatoms.Mostoftheinvestig8tionsconcernedthedoublyexcitedstatesinwhichoneofthetwovalenceelectronsishighlyexcitedandtheotherisweaklyexcited[1].Inthecasewhenbothvalenceelectronarehighlyexcited(doubleRydbergstates),onlyafewresultswereobtainedduetothelimitutioninexPerimentaltech-nique['j.ThelimitationarosefromvariousaSpectS.First,duringthesequentiallaserex-citationofdoubleRydbergstatesw…     

PuH2分子激发态的外场效应

采用密度泛函(DFT)方法B3LYP/Gen,在Pu为SDD基组、H为6-311 G**基组水平上优化得到了分子轴方向不同电偶极场(-0.005~0.005 a.u.)作用下,二氢化钚的基态电子状态、几何结构和分子总能量.在优化构型下用同样的基组采用含时密度泛函(TDDFT)方法(TD-B3LYP)研究了同样外电场条件下对二氢化钚的激发能、振子强度、自旋污染和Pu原子正电荷的影响.计算结果表明,分子几何构型与电场大小和方向呈现较强的依赖,H-Pu-H的角度线性减少,分子总能量线性减少;自旋污染随电场增加线性增加;Pu原子正电荷随电场增加而线性减小;激发能随电场强度增加而减小,且对电场方向的依赖呈现近似对称性,满足Grozema关系.电场对振子强度的影响比较复杂,但仍满足跃迁选择定则.     

Loading rate of Yb<Superscript>+</Superscript> loaded through photoionization in radiofrequency ion trap

We investigate the loading rate of Yb⁺ ions loaded through photoionization in a radiofrequency trap. The absolute or relative number of the loaded trapped ions is measured by use of an electric resonance of the secular motion. This method is applicable even in the presence of anharmonicity. In two-color photoionization, where the first-excitation laser drives the ¹S₀–¹P₁ transition in the Yb atom and the second one ionizes the atom from the ¹P₁ state, the loading rate is at its highest by the excitation of the ionization potential. A similar loading rate is observed at the second-laser wavelength around 369.5 nm, which is the wavelength for the cooling transition of Yb⁺. We estimate the loading cross section to be 40(15) Mb for the two-color excitation of the ionization potential. The excitation of the Yb atoms in the Rydberg states is detected by the enhancement of the loading rate. By irradiation with only the first-excitation laser, Yb⁺ is produced at a rate three orders of magnitude smaller than that when the non-resonant two-photon absorption from the ¹P₁ state is the dominant process. We also measure the charge-exchange rate between Yb⁺ and Yb, and discuss its effect on isotope-selective photoionization loading.     

Yb原子高激发态的斯塔克光谱

采用ππ偏振激光，通过两步激发和光电离方法，在０－１５４Ｖ／ｃｍ电场范围内，测定了Ｙｂ原子ｎ－１８附近ｍ＝０的斯塔克光谱，首次把包含斯塔克效应的能量矩阵对角化方法推广到Ｙｂ原子，所获得的理论斯塔克图与实验结果基本符合，观察到低场中斯塔克簇随电场增加呈现线性结构以及＾１Ｐ１态与斯塔克簇在抗交叉过程中振子强度发生转移的现象，讨论了结构与量子亏损的关系。     

Direct excitation of the forbidden clock transition in neutral 174Yb atoms confined to an optical lattice

We report direct single-laser excitation of the strictly forbidden (6s2)1S0 <--> (6s6p)3P0 clock transition in 174Yb atoms confined to a 1D optical lattice. A small (approximately 1.2 mT) static magnetic field was used to induce a nonzero electric dipole transition probability between the clock states at 578.42 nm. Narrow resonance linewidths of 20 Hz (FWHM) with high contrast were observed, demonstrating a resonance quality factor of 2.6 x 10(13). The previously unknown ac Stark shift-canceling (magic) wavelength was determined to be 759.35 +/- 0.02 nm. This method for using the metrologically superior even isotope can be easily implemented in current Yb and Sr lattice clocks and can create new clock possibilities in other alkaline-earth-like atoms such as Mg and Ca.     

Determination of static dipole polarizabilities of Yb atom

We determine the static values of the scalar and tensor dipole polarizabilities of the ground, 6s6p~3P_0~o, and 6s6p~3P_1~o states of the Yb atom. These results can be useful in many experiments undertaken using this atom. We employed a combined configuration interaction(CI) method and a second-order many-body perturbation theory(MBPT) to evaluate energies and electric dipole(E1) matrix elements of many low-lying excited states of the above atom. These values are compared with the other available theoretical calculations and experimental values. By combining these E1 matrix elements with the experimental excitation energies, we estimate the dominant valence correlation contributions to the dipole polarizabilities of the above states. The core contribution is obtained from the finite field approach. We also compare these values with the other theoretical results as there are no precise experimental values that are available for these properties.     

环境辐射对原子高激发能级Stark态寿命的影响

在外电场中用激光两步激发使Na原子在待测Stark态（n=17，m=0）上实现布居．用延迟脉冲场电离方法测量了部分Stark态的寿命及环境黑体辐射对其实际寿命的影响，并与理论计算值作了比较．实验和计算表明：对n=17的Stark簇各能态，室温下环境黑体辐射引起的受激跃迁对其寿命的影响与自发辐射跃迁已达同一数量级．寿命越长的Stark态，黑体辐射的影响程度越大，这一因素连同Stark混合效应均使同一Stark簇内各能态实际寿命的差异变小． 关键词：     

原子两步激发禁戒态寿命及环境辐射的影响

在167V/cm的静电场中,借助Stark态混合使Na原子两步激发禁戒的np态得到布居.用延迟脉冲场电离方法测定了np(n=19-23)态的寿命值,并与理论计算值作了比较.讨论了外电场及环境辐射等因素对高激发态寿命的影响.     

Excited atomic and molecular states in strong electromagnetic fields

Large changes in atomic and molecular structure can occur when strong static or oscillating electromagnetic fields are present. Such fields also can ionize atoms. Strong oscillating fields induced multiphoton transitions between bound states as well as to the continuum. What is known about these phenomena is reviewed, with emphasis on theories and experiments concerned with the field-sensitive excited and highly-excited states.     

Electric-field-modified Feshbach resonances in ultracold atom–molecule collision

We present a detailed analysis of near zero-energy Feshbach resonances in ultracold collisions of atom and molecule,taking the He–PH system as an example, subject to superimposed electric and magnetic static fields. We find that the electric field can induce Feshbach resonance which cannot occur when only a magnetic field is applied, through couplings of the adjacent rotational states of different parities. We show that the electric field can shift the position of the magnetic Feshbach resonance, and change the amplitude of resonance significantly. Finally, we demonstrate that, for narrow magnetic Feshbach resonance as in most cases of ultracold atom–molecule collision, the electric field may be used to modulate the resonance, because the width of resonance in electric field scale is relatively larger than that in magnetic field scale.     

外电场下二氧化锆的分子结构及其特性

对O原子采用6-311++G*基组,Zr原子采用aug-cc-pVTZ-PP基组,利用密度泛函(B3P86)方法优化得到了ZrO2分子的稳定构型,并研究了不同外电场(0—0.025 a.u.)作用下ZrO2基态分子键长、能量、电荷分布、偶极矩和能级的变化规律.在优化构型的基础上,利用含时密度泛函(TD-B3P86)方法研究了ZrO2分子在外电场作用下前6个激发态的激发能、跃迁波长和振子强度的激发特性.研究结果表明:随着电场强度的增大,Zr—2O的键长增大,而Zr—3O的键长均匀减少,总能量降低,偶极矩增大;最高占据轨道能量基本保持不变,最低未占据轨道和能隙均减小.电场的增大使得激发能减小,各个激发态跃迁波长均发生不同程度的红移现象,因而,利用外电场可以控制ZrO2的发光光谱范围在可见-红外区域扩展.     

Dressed atoms in flight through a periodic crystal field: X-VUV double resonance

We report the Autler-Townes doublet demonstrating a novel type of coherent interaction of atoms not with photons but with a periodic crystal field when the atom is in flight through a crystal at high velocity. It was observed by the nonoptical X-VUV (vacuum-ultraviolet) double resonance of three-dimensional resonant coherent excitation with good coherence. The states strongly coupled in the VUV region were probed by the excitation in the x-ray region. The characteristic spectra are well interpreted by an analogy of the dressed atom concept often adopted for the atom-photon interaction.     

Yb原子高激发能级的跃迁特性

采用“类氢”模型,用数值积分方法计算了Yb原子部分高激发Rydberg态和Stark态的自发跃迁概率,及环境黑体辐射引起的受激跃迁概率,并与采用延迟脉冲场电离方法对相应态的测量结果做了比较.选取典型的初始态,测量了环境黑体辐射引起的受激跃迁对周围能级的再布居特性,并给出了理论解释.对“类氢”模型应用于复杂原子的适用性进行了分析. 关键词：     

用激光共振电离光谱测定铈原子奇宇称高激发态(Ⅰ):32 042～34 575 cm-1

激光共振电离光谱是一种十分适合于高能量区重元素复杂原子结构研究的技术。为寻找原子最佳的共振电离通道，利用这一技术对铈原子奇宇称高激发态进行了研究。在32042－34575cm^-1范围内，用两步共振激发和非共振电离方法，首次观察到了83条铈原子奇宇称高激发态能级，测量了这些新能级的能量和给出了可能的总角动量J值。     

氯乙烯在外电场下的激发态结构研究

采用密度泛函B3P86方法在6-311G基组上优化了不同外电场作用下氯乙烯分子的基态几何结构、电偶极矩和分子的总能量,然后利用杂化CIS-DFT方法(CIS-B3P86)在相同基组下探讨了无电场时氯乙烯分子前9个激发态的激发能、波长和振子强度和外电场对氯乙烯分子激发态的影响规律.结果表明,分子的几何构型与外电场大小有着强烈的依赖关系.随着外电场的增大,分子总能量先增大后减小,电偶极矩μ先减小后增大.激发能随电场增加快速减小,表明在外电场作用下,氯乙烯分子易于激发和离解.激发态波长随电场的增大而不断增大,且其电子跃迁光谱都集中在紫外区.     

Observation of the Dipole Blockade Effect in Detecting Rydberg Atoms by the Selective Field Ionization Method

The dipole blockade effect at laser excitation of mesoscopic ensembles of Rydberg atoms lies in the fact that the excitation of one atom to a Rydberg state blocks the excitation of other atoms due to the shift in the collective energy levels of interacting Rydberg atoms. It is used to obtain the entangled qubit states based on single neutral atoms in optical traps. In this paper, we present our experimental results on the observation of the dipole blockade for mesoscopic ensembles of 1–5 atoms when they are detected by the selective field ionization method. We have investigated the spectra of the three-photon laser excitation 5S1/2 → 5P3/2 → 6S1/2 → nP3/2 of cold Rydberg Rb atoms in a magneto-optical trap. We have found that for mesoscopic ensembles this method allows only a partial dipole blockage to be observed. This is most likely related to the presence of parasitic electric fields reducing the interaction energy of Rydberg atoms, the decrease in the probability of detecting high states, and the strong angular dependence of the interaction energy of Rydberg atoms in a single interaction volume.     

Electric-field induced dipole blockade with Rydberg atoms

High resolution laser Stark excitation of np (60相似文献