类铷W37+离子双电子复合速率系数的理论研究

 利用全相对论组态相互作用理论方法,研究了类铷W³⁷⁺离子从基组态3s²3p⁶3d¹⁰4s²4p⁶4d经过双激发态(3s²3p⁶3d¹⁰4s²4p⁶4d)^-1nln′l′(n,n′=4,5)的双电子复合过程,得到了该离子在温度为1~5×10⁴ eV范围内的总双电子复合速率系数。分析比较了不同电子激发的双电子复合速率系数,结果表明:4p电子激发的双电子复合速率系数在低温时给出了主要贡献,而3d的贡献在高温时突出。由于强组态相互作用,两电子一光子跃迁对双电子复合速率系数的贡献不可忽略,其中辐射跃迁4p⁵4d5d5f-4p⁶4f5d的贡献是双激发态4p⁵4d5d5f总的双电子复合速率系数的5%。对双电子复合、辐射复合以及三体复合速率系数的比较表明,在所研究的温度范围内双电子复合速率系数最大。     

DIELECTRONIC RECOMBINATION OF Co-LIKE Ag AND Ta IONS

Ab initio calculations of the rate coefficients for dielectronic recombination (DR) of Co-like Ag and Ta ions are performed based on Cowan's quasi-relativistic multi-configuration Hartree－Fock code. Co-like (3s ²3p⁶3d¹⁰)^-1 configurations and Ni-like (3s²3p⁶3d¹⁰)^-24l4l' autoionization configurations are included in the present calculation. Because of the extensive distribution of autoionization state energy levels, the DR rate coefficients cannot be reproduced or interpolated by a simple analytical formula, such as the Burgess－Merts formula, or the Hagelstein approximation. We propose to use multi-set Hagelstein parameters, which is convenient in practice and can reproduce well the ab initio calculated DR rate coefficients.     

Dielectronic recombination rate coefficients of Ni-like barium and tungsten

Ab initio calculations of the total dielectronic recombination (DR) rate coefficient of Ni-like barium () and tungsten () in the ground state have been performed using the HULLAC atomic code package. Resonant and nonresonant stabilizing radiative transitions are included. Collisional transitions following electron capture are neglected. The present level-by-level calculations include the DR contributions of all of the levels (over 17000) in the Cu-like inner-shell excited configurations 3d ⁹ 4ln'l' (), 3p ⁵ 3d ¹⁰ 4ln'l' (), and 3s3p ⁶ 3d ¹⁰ 4ln'l' (). For both ions, the configuration complexes with a hole in the 3p inner shell contribute almost 10% to the total DR rate coefficient, while the complexes with a hole in the 3s inner shell contribute about 1%. The converging contributions of the 3d ⁹ 4ln'l' (n' > 9) configurations are evaluated by applying the complex-by-complex extrapolation method and are found to comprise up to about 20% of the total DR rate coefficients throughout a wide electron temperature range. The total DR rate coefficients are fitted to an easy-to-use analytic expression which reproduces the original data with an accuracy of about 2% or better in a very wide temperature range. Received: 1 February 1999     

Dielectronic recombination rate coefficients for the Ni ${\sf I}$ isoelectronic sequence

Ab initio calculations of the total dielectronic recombination (DR) rate coefficients for thirteen ions along the NiI isoelectronic sequence in the ground state (Kr⁸⁺, Mo¹⁴⁺, Ag¹⁹⁺, Sn²²⁺, Xe²⁶⁺, Nd³²⁺, Gd³⁶⁺, Yb⁴²⁺, W⁴⁶⁺, Au⁵¹⁺, Pb⁵⁴⁺, At⁵⁷⁺, and U⁶⁴⁺) have been performed using the flexible atomic code. The level-by-level calculations are performed for evaluating the DR contributions through the relevant Cu-like autoionizing inner-shell excited 3l¹⁷4l^′n^′′l^′′ and 3l¹⁷5l^′n^′′l^′′ configuration complexes with n^′′ ≤15, which are associated with Δn=1 and Δn=2 core-excitations, respectively. The usual (n^′′)^-3 scaling law is found to be invalid for low-Z ions. A level-by-level extrapolation procedure is employed to obtain the contributions through higher n^′′ complexes. The decays to autoionizing levels followed possibly by radiative cascades could enlarge the rates at relatively high temperature by a factor up to about 23%. For the whole isoelectronic ions the contributions from 3s²3p⁶3d⁹ 4l^′n^′′l^′′ dominate the total DR rates while the contributions from the 3s²3p⁶3d⁹ 5l^′n^′′l^′′ configuration complexes are about 10-20% at relatively high temperature. On the basis of the calculated results, a general analytic formula for the total DR rate coefficients of all the ions with 36≤Z ≤92 along the NiI isoelectronic sequence is constructed. The comparisons of the rates obtained from the general formula with those from the detailed calculations show that the formula is of high precision, generally better than 3% accuracy for electron temperatures kT≥0.1E_I, where E_I is the ionization energy of the Cu-like ion. The present DR rates at temperature above 1.0E_I are larger than the previously published data by a factor above 30%. The commonly used semiempirical formula proposed by Burgess and modified by Merts may overestimate the rates at high temperature by a factor of about 2 for low-Z ions.     

Luminescence study of the 4f5d configuration of Nd in LiYF4, LiLuF4 and BaY2F8 crystals

Ultraviolet fluorescence of Nd³⁺ ions induced by triphotonic excitation process was studied in Nd-doped LiYF₄, LiLuF₄ and BaY₂F₈ crystals using a technique of time-resolved spectroscopy. The observed ultraviolet luminescence was due to transitions between the bottom of 4f²5d configuration and 4f³ states of Nd³⁺ ions. Narrow emission lines superposed to the broadband emissions were observed. A detailed analysis of luminescence spectrum revealed that the narrow emissions are due to parity and spin allowed radiative transitions from the Stark levels of ⁴K_11/2(5d) state created by the electrostatic interaction between the 5d electron and the two electrons of the 4f² configuration. The narrow emissions are related to the high spin state (S=3/2) which gives f-f characteristics to the f-d broadband emissions. The narrow emissions superposed to the wide emission correspond to 18%, 34% and 43% of the integrated broadband emission at 262 nm observed in LiYF₄, LiLuF₄ and BaY₂F₈ crystals, respectively. Although the 5d-4f² interaction is observed to be weaker than 5d-crystal field interaction, it is stronger enough to select only the radiative transitions from 4f²5d configuration to 4f³ states that preserves the total spin S=3/2.     

Gd激光等离子体的双电子复合过程研究

在自旋-轨道劈裂阵模型下,通过类铜的内壳层激发组态计算了类镍Gd的双电子复合速率系数,其中考虑了共振和非共振辐射平衡跃迁对自电离能级的影响,而忽略了因碰撞跃迁引起的电子俘获,非共振辐射平衡跃迁在低电子温度条件下主要影响双电子复合过程;本文讨论了双电子复合系数及双电子伴线强度比随电子温度的变化.     

氙激光等离子体的双电子复合过程研究(英文)

在自旋-轨道劈裂阵模型下,通过类铜的内壳层激发组态计算了类镍氙的双电子复合速率系数,其中考虑了共振和非共振辐射平衡跃迁对自电离能级的影响,而忽略了因碰撞跃迁引起的电子俘获,非共振辐射平衡跃迁在低电子温度条件下主要影响双电子复合过程;本文讨论了双电子复合系数及双电子伴线强度比随电子温度的变化.     

Spectra and oscillator strengths of 3p63d9--3p53d10 and 3p63d9--3p63d84p transitions for cobalt-like Sn23+ ion

This paper calculates the spectra and oscillator strengths for highly ionized cobalt-like Sn23+ ions 3p63d9 3p53d10,3p63d9 3p63d84p transitions by using a multi-configuration self-consistent field method program together with the proposed fitting formula.The calculations have a good agreement with observations.     

Total dielectronic recombination rate coefficient for Co-like tungsten

Ab initio calculation of the total dielectronic recombination (DR) rate coefficient from the ground state 3s²3p⁶3d⁹(J=5/2) of Co-like tungsten is performed employing the relativistic distorted-wave approximation with configuration-interaction. The DR contributions mainly come from complex series 3d⁸4ln′l′. The complex series 3p⁵3d¹⁰n′l′, 3p⁵3d⁹4ln′l′ and 3d⁸5ln′l′ also contribute significantly to the total DR rates at relatively high electron temperatures. The l′ and n′ dependences of the partial rate coefficient are investigated. The inclusion of decays into autoionizing levels followed by radiative cascades (DAC) enlarges the total DR rate coefficients by a factor of about 10%. The level-by-level extrapolation method is developed to include DAC effects. The total DR rate coefficients are fitted to an empirical formula. It is shown that at temperatures above 2.5 keV the Burgess-Merts (BM) semiempirical formula can provide DR results with an accuracy of about 15%, whereas at electron temperatures below 100 eV it underestimates the DR rate coefficients by up to a few orders of magnitude and its temperature dependence is completely inadequate. The comparison of the results for Ni-like and Co-like tungsten shows that these two sets of DR rate coefficients are very close in magnitude at relatively high electron temperatures.     

掺铒硅发光的晶场分裂

测量了掺铒硅的高分辨光致发光光谱，得到9条铒发光分裂谱线.利用群对称理论指出9条谱线来自Er³⁺中⁴I_13/2到⁴I_15/2光跃迁在T_d晶场下的分裂.Er³⁺的第一激发态⁴I_13/2最低能量的两个Stark能级为Γ₈，Γ₆(能量递增)，它们到基态⁴关键词：     

The dielectronic recombination process in laser-produced Au plasmas

The calculations of the rate coefficients for dielectronic recombination (DR) along the NiI isoelectronic sequence in the ground state Au^{51+} through Cu-like 3d^9nln′f (n,n′=4,5,6) inner-shell excited configurations are performed using the spin-orbit-split array (SOSA) model. Resonant and nonresonant radiative stabilizing transitions and decays to autoionizing levels followed by radiative cascades are included. Collisional transitions following electron capture are neglected. The trend of the DR rate coefficients and the ratio of dielectronic satellite lines intensities with the change of the electron temperature are discussed.     

Theoretical transition probabilities and lifetimes in nickel-like Se,Y and Sn ions

The 17 levels of the 3 d ¹⁰ , 3 d ⁹ 4 s and 3 d ⁹ 4 p configurations, and the electric-dipole transitions among these levels are calculated for the three nickel-like ions Se⁶⁺, Y¹¹⁺ and Sn²²⁺ by using large-scale multiconfiguration Dirac-Fock wavefunctions. From these computations, the excitation energies and transition probabilities as well as the lifetimes of 3 d ⁹ 4 p levels are derived, including all dominant effects of relativity, correlation and of the rearrangement of the electron density within the same framework. Comparison is made with the scarce number of experimental data and previous semi-empirical computations.     

Spectroscopic studies of erbium-doped potassium-lead double chloride crystals KPb<Subscript>2</Subscript>Cl<Subscript>5</Subscript>:Er<Superscript>3+</Superscript>: 1. Optical spectra and relaxation of excited states of the erbium ion in potassium-lead double chloride crystals

Optical spectra, intensities of radiative and nonradiative transitions, and luminescence kinetics in erbium-doped potassium-lead double chloride crystals KPb₂Cl₅:Er³⁺s(KPC:Er³⁺) were investigated. The crystals were grown by the Bridgman-Stockbarger method. Their absorption and luminescence spectra were studied experimentally. The crystal-matrix absorption edge was determined at 80 and 300 K. Intensity parameters, radiative transition probabilities, branching ratios, and nonradiative relaxation rates were estimated by the Judd-Ofelt method. The luminescence kinetics from the emitting levels ⁴ G _11/2, ² G _9/2, ⁴ S _3/2, and ⁴ F _9/2 upon selective excitation was studied.     

High-temperature VUV spectroscopy of KYF4 crystals doped with Nd3+, Er3+ and Tm3+ ions

Thermal quenching of 5d-4f luminescence from Nd³⁺, Er³⁺ and Tm³⁺ ions doped into KYF₄ crystals has been investigated in the temperature range up to ∼750 K where this luminescence is completely quenched. The obtained temperatures of thermal quenching (T_q) are ∼270, 495, 450 K for Nd³⁺, Er³⁺, Tm³⁺, respectively. At high temperatures, thermal quenching of 5d-4f luminescence from Nd³⁺ and Er³⁺ is accompanied by the appearance of 4f-4f luminescence from the lower-energy 4f levels. It has been shown that the dominating mechanism of thermal quenching for Nd³⁺ and Er³⁺ ions is thermally stimulated non-radiative transitions (intersystem crossing) from the 5d states to lower-energy 4f levels, namely ²G(2)_9/2 and ²F(2)_7/2, respectively, whereas for the Tm³⁺ ion, thermally stimulated ionization of 5d electrons to the conduction band states is responsible for thermal quenching of 5d-4f luminescence. The energy gap between the lowest Tm³⁺ 5d level and the bottom of the KYF₄ conduction band has been estimated to be 0.66 eV.     

Radiative constants in the spectra of ions of the krypton isoelectronic sequence

The probabilities of the 4p ⁶,4p ⁵5p→4p ⁵(4d+5s) radiative transitions and the radiative lifetimes of the 4p ⁵4d,4p ⁵5s, and 4p ⁵5p levels are calculated semiempirically for the RbII-MoVII isoelectronic sequence.     

4d 95p 2 configuration in the spectra of in III-Te VI

The radiative 4d ¹⁰5p-4d ⁹5p ² transitions in the spectra of the In III, Sn IV, Sb V and Te VI, ions, belonging to the silver isoelectronic sequence, have been investigated in the range 250–600 Å with high resolution. The energies of most levels of the 4d ⁹5p ² configuration with J = 1/2, 3/2, and 5/2, involved in the transitions to the 4d ¹⁰5p configuration, are found. Along the isoelectronic sequence, the 4d ⁹5p ² configuration passes from the position below the ionization limit 4d ¹⁰ in Te VI to the position above this limit in In III with corresponding autoionization effects. The autoionization widths of levels are measured. The data obtained are compared with the results of calculations by the Hartree-Fock and semiempirical methods.     

Resonant photoemission from SmS(100)

A strong, sharp resonance enhancement of 4f photoemission has been observed on SmS(100) surfaces for photon energies in the region of the 4d-4f transitions at about 126 eV. The discrete final state reached via the excitation hν+4d¹⁰4f⁶→4d⁹4f⁷ autoionizes primarely via a super Coster-Kronig transition of the type 4d⁹4f⁷→4d¹⁰4f⁵ + unbound electron. Other decay channels, e.g, Sm 5p emission, as well as a surface induced binding energy shift in the Sm³⁺ final state are identified and discussed.     

类氦离子的KLL双电子复合过程的相对论理论研究

在相对论多组态Dirac-Fock理论基础上，发展了计算双电子复合截面的程序.并以类锂C³⁺，Ar¹⁵⁺，Kr³³⁺和U⁸⁹⁺等离子为例，详细计算了共振双激发态1s2l2l′的辐射衰变率、Auger衰变率及相应的双电子复合截面.对于C⁴⁺，Ar^l6+和Kr³⁴⁺离子的结果与已有的计算和实验结果都能很好地符合；对于U⁹⁰⁺离子，则重点 关键词： 双电子复合 截面 MCDF     

Dielectronic Recombination Rate Coefficients for Nickel-like Ytterbium

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Electron energy-loss spectroscopy of UHV-cleaved NiO (100) surfaces

Electron energy-loss spectroscopy of ～ 200 eV electrons has been applied to the study of the electronic states of clean NiO (100) surfaces. Initial attempt has been made on the identification of observed peaks, and they are attributed to the one-electronic transitions (O^2-2p → Ni²⁺3d, 4s and 4p; Ni²⁺3d → 4p, 3p → 3d and 4s), and the collective excitations (bulk plasmons of O^2-2p, Ni²⁺3d electrons, and coupled 2p and 3d electrons).