类铝离子钟跃迁能级的超精细结构常数和朗德g因子

本文利用多组态Dirac-Hartree-Fock方法计算了类铝等电子序列从Si⁺到Kr²³⁺离子基组态3s²3p ²P_{1/2, 3/2}能级的超精细结构常数和朗德g因子.通过系统评估电子关联效应对Si⁺和Co¹⁴⁺离子中所关心原子参数的影响,尤其是与内壳层电子相关的关联效应,构建了可靠精确的计算模型,除Si⁺离子外,超精细结构常数和g因子的计算误差分别控制在1%左右和10^–5的量级.此外,进一步分析了超精细结构常数中电子部分矩阵元和g因子随原子序数Z的变化规律,并拟合了这些物理量与Z的定量依赖关系,利用拟合公式可以快速计算类铝离子在14≤Z≤54区间内任意同位素的超精细结构常数和g因子.     

重离子冷却储存环CSRm双电子复合实验研究类锂36,40Ar15+离子同位素移动

配备电子冷却装置的重离子储存环为开展高电荷态离子的双电子复合（dielectronic recombination,DR）精密谱学研究提供了绝佳的实验平台。本工作在兰州重离子加速器冷却储存环主环（HIRFL-CSRm）上开展了类锂36,40Ar15+离子的双电子复合实验,实验观测了电子-离子质心系能量范围为0~35 eV的双电子复合速率系数谱。通过外推法获得了36,40Ar15+离子2s_1/2→2p_1/2和2s_1/2→2p_3/2的跃迁能量。同时利用GRASP2K程序理论计算了36,40Ar15+离子2s_1/2→2p_1/2和2s_1/2→2p_3/2跃迁的质量移动因子和场移动因子,进而得到双电子复合谱的同位素移动值。36,40Ar15+离子2s_1/2→2p_1/2和2s_1/2→2p_3/2同位素移动分别为0.861 meV和0.868 meV。它们均小于目前CSRm上双电子复合实验的实验分辨为~10 meV,进而解释了实验测量的DR谱上未能观察到同位素移动的原因。然而,高电荷态离子的同位素移动场效应与原子序数Z5成正比,因此,在重离子加速器冷却储存环实验环（HIRFL-CSRe）以及未来大型加速器--强流重离子加速器装置（HIAF）上有望通过DR精密谱学方法研究高电荷态重离子甚至放射性离子的同位素移动,进而获得相关原子核的核电荷半径等信息。The cooler storage ring is equipped with an electron-cooler. It is an excellent experimental platform for dielectronic recombination (DR) experiment of highly-charged ions. In this paper, the dielectronic recombination experiments of lithium-like Ar15+ ions with mass number 36 and 40 are conducted at the HIRFL-CSRm(main ring of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou). The experimental electron-ion collision energy scale is from 0 eV to 35 eV. Extrapolation method is exploited to obtain the excitation energies of transitions 2s_1/2→2p_1/2 and 2s_1/2→2p_3/2 of the 36,40Ar15+ ions from experimental data. Meanwhile, GRASP2K program is utilized to calculate the mass shift factors and field shift factors of 36,40Ar15+ ions for 2s_1/2→2p_1/2 and 2s_1/2→2p_3/2 transitions to obtain isotope shifts in DR spectra. In theoretical calculation, isotope shifts of 36,40Ar15+ ions corresponding to 2s_1/2→2p_1/2 and 2s_1/2→2p_3/2 are 0.861 meV and 0.868 meV, respectively. They are both less than the experimental precision (~10 meV) of these dielectronic recombination experiments at the CSRm, which explains that isotope shifts cannot be distinguished from the experimental dielectronic recombination spectra. However, the field shift of highly-charged ions is proportional to Z5. In the future, the dielectronic recombination experiments of highly-charged heavy ions even radioactive ions will be conducted at the HIRFL-CSRe (experimental ring of the Cooling Storage Ring of Heavy Ion Research Facility in Lanzhou) and the future large accelerator facility--HIAF(High intensity Heavy-ion Accelerator Facility) to measure isotope shifts to obtain the nuclear charge radius information.     

原子核的有限体积效应对高离化态离子能级和波函数的影响

在相对论理论框架下,分别在点电荷和两参数Fermi核模型近似下计算了高离化态类氢离子（Z=80—112）n=1—3壳层的波函数和能级. 分析了核有限体积效应对它们的影响. 在此基础上,给出了核有限体积效应对原子能级的修正公式. 同时,还进一步讨论了相对论效应和核有限体积效应之间的相互影响,发现对高Z元素相对论效应与核有限体积效应之间有很强的耦合. 关键词： 原子核有限体积效应 高离化态离子 相对论效应     

NⅡ离子2p4f—2p3d辐射跃迁概率的理论研究

在全相对论理论框架下，利用多组态Dirac-Fock(MCDF)方法，系统计算了NⅡ离子2p4f—2p3d的辐射跃迁概率，得到的结果与已有实验值符合很好.具体计算中，详细分析了相对论效应、电子关联、弛豫效应、Breit相互作用和量子电动力学(QED)效应对能级精细结构及辐射跃迁概率的影响.结果表明：相对论效应、电子关联和弛豫效应对NⅡ 2p4f-2p3d辐射跃迁概率有很重要的影响,考虑了这些效应后计算值得到明显改善.     

Resonance Energies,Absorption Oscillator Strengths and Ionization Potentials for the Element Hassium （Z = 108）

On the basis of successfully predicting low-lying energy levels for the element fermium （Z = 100）, we calculate the resonance energies, absorption oscillator strengths and the first ionization potential of the element hassium （Z = 108） by taking important relativistic and improved electron correlation effects into account using the multiconfiguration Dirac Fock method. These calculations are carried out with the aim of assisting experimental investigations of hassium.     

M1 transition energy and rate in the ground configuration of Ag-like ions with 62 ≤ Z ≤ 94

Systematic calculations and assessments are performed for the magnetic dipole(M1)transition energies and rates between the ²F^o_5/2,7/2 levels in the ground configuration 4d104f along the Ag-like isoelectronic sequence with 62≤Z≤94 based on the second-order many-body perturbation theory implemented in the Flexible Atomic Code.The electron correlations,Breit interaction and quantum electrodynamics effects are taken into account in the present calculations.The accuracy and reliability of our results are evaluated through comprehensive comparisons with available measurements and other theoretical results.For transition energies,our results are in good agreement with the recent experimental data obtained from the electron beam ion traps within 0.18%.The maximum discrepancy between our results and those obtained with the large-scale multiconfiguration Dirac–Hartee–Fock calculations by Grumer et al.[Phys.Rev.A 89062501(2014)]is less than 0.13%along the isoelectronic sequence.Furthermore,the corresponding M1 transition rates are also reported.The present results can be used as the benchmark and useful for spectra simulation and diagnostics of astrophysical and fusion plasmas.     

Hg~+离子5d~(10)6s ~2S_(1/2)→5d~96s~2 ~2D_(5/2)钟跃迁同位素位移和超精细结构的理论研究

本文首先在Dirac-Hartree-Fock近似下理论评估了Hg~+离子5d~(10)6s ~2S_(1/2)→5d~96s~2 ~2D_(5/2)钟跃迁的质量位移(mass shift, MS)和场位移(field shift, FS)在其同位素位移(isotope shift, IS)中的相对贡献,发现MS远小于FS而可以被忽略.在此基础上,通过系统地考虑该原子体系中主要的电子关联效应,计算了这条钟跃迁FS的精确值以及涉及到的上下两个能级的超精细结构常数,并得到了几种稳定汞同位素离子该跃迁的IS和超精细结构分裂.其中,计算的~(199)Hg~+和~(198)Hg~+离子之间的钟跃迁频率偏移与已有实验测量值相比误差为2%左右.最终,本文给出了汞离子7种常见同位素该谱线的绝对频率值,为实验上的谱线测量提供了有效的理论依据.     

Experimental Determination of the Landé g-Factors for 5s~2 ~1S and 5s5p ~3P States of the ~(87)Sr Atom

We present an experimental determination on the Lande g-factors for the 5 s~2 ~1 S_0 and 5 s5 p ~3 P_0 states in ultra-cold atomic systems, which is important for evaluating the Zeeman shift of the clock transition in the ~(87)Sr optical lattice clock. The Zeeman shift of the 5 s5 p ~3 P_0-5 s~2 ~1 S_0 forbidden transition is measured with the π-polarized andσ~±-polarized interrogations at different magnetic field strengths. Moreover, in the g-factor measurement with the σ~±-transition spectra, it is unnecessary to calibrate the external magnetic field. By this means, the ground state 5 s~2 ~1 S_0 g-factor for the ~(87)Sr atom is-1.306(52) ×10~(-4), which is the first experimental determination to the best of our knowledge, and the result matches very well with the theoretical estimation. The differential g-factorδg between the 5 s5 p~3 P_0 state and the 5 s~2 ~1 S_0 state of the ~(87)Sr atoms is measured in the experiment as well,which are-7.67(36) ×10~(-5) with π-transition spectra and-7.72(43) X 10-5 with σ~±-transition spectra, in good agreement with the previous report [Phys. Rev. A 76(2007) 022510]. This work can also be used for determining the differential g-factor of the clock states for the optical clocks based on other atoms.     

Theoretical calculation of the quadratic Zeeman shift coefficient of the 3P0o clock state for strontium optical lattice clock

In the weak-magnetic-field approximation, we derived an expression of quadratic Zeeman shift coefficient of $^3P^{\rm o}_0$ clock state for $^{88}$Sr and $^{87}$Sr atoms. By using this formula and the multi-configuration Dirac-Hartree-Fock theory, the quadratic Zeeman shift coefficients were calculated. The calculated values $C_2$ = $-23.38(5)$ MHz/T$^2$ for $^{88}$Sr and the $^3P^{\rm o}_0$, $F = 9/2$, $M_F = \pm9/2$ clock states for $^{87}$Sr agree well with the other available theoretical and experimental values, especially the most accurate measurement recently. In addition, the calculated values of the $^3P^{\rm o}_0$, $F = 9/2$, $M_F = \pm9/2$ clock states were also determined in our $^{87}$Sr optical lattice clock. The consistency with measurements verifies the validation of our calculation model. Our theory is also useful to evaluate the second-order Zeeman shift of the clock transition, for example, the new proposed $^1S_0$, $F = 9/2$, $M_F = \pm5/2$-${}^3P^{\rm o}_0$, $F = 9/2$, $M_F = \pm3/2$ transitions.     

电子关联对类铍离子1s~22s2p~3P_(0,1)能级的超精细结构常数的影响

基于MCDF方法系统地计算了Z=20~83范围内24个类铍离子的1s22s2p3P0,1态的精细结构,得到了与其它理论和实验符合很好的结果.在此基础上,进一步计算了超精细结构对角及非对角常数,并分析了不同电子关联效应和Breit相互作用对它们的影响.