Opacity calculations for high-Z plasma in non-local thermodynamic equilibrium

Opacity of high-Z element plasma in non-local thermodynamic equilibrium (NLTE) is calculated. In the calculation, a collisional radiative model in detailed-configuration-accounting (DCA) is applied to population calculations for NLTE plasmas. Configuration-averaged rate coefficients that needed in the rate equations are obtained based on the first order perturbation theory. The Hatree-Fock-Slater self-consistent-field method is used to calculate the electron wave functions. The spin-orbit splitting is included in the spectrum calculations. The unresolved transition array method is used in the opacity calculations. The calculated frequency-dependent opacity of high-Z plasma Lu is presented. The comparison shows that the present spectrum agrees with another theoretical result well except that the present one shifts a little to the lower energy due to its lower mean ionization stage. The effects of highly doubly excited states on ionization balance and on the opacity are investigated. The mean ionization stage increases more than three stages when doubly excited states 5l6l′ and 5l5l′ are not included in the population calculations and the absorption spectrum also shifts to the higher energy.     

类铍Ar^14＋和类镁Ar^6＋离子双激发态能级的计算

用相态相互作用方法计算了类铍Ａｒ＾１４＋离子双激发态１ｓ＾２３ｌ３ｌ＇和类镁Ａｒ＾６＋离子双激发态１ｓ＾２２ｓ＾２２ｐ＾６４ｌ４ｌ＇的能级。两个外层电子与内层原子实１ｓ＾２或１ｓ＾２２ｓ＾２２ｐ＾６电子的作用用模型势表不。Ａｒ＾１４＋的双激发态可用量子数Ｋ，Ｔ和Ａ标记，而Ａｒ＾６＋的某些组态却不能用上述量子数表示。     

W44+ 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方法,详细研究了W44+ 离子从基组态3s23p63d104s2俘获一个电子形成双激发态(3s23p63d104s2)nln′l′(n = 4 ~ 6,n′= 4 ~7) 的双电子复合(DR) 过程。通过比较不同壳层电子激发的DR 速率系数,得知4s 电子激发和3d 电子激发的DR 速率系数分别在低温和中高温度时给出了主要贡献,得到了主要的电子激发DR通道。在1 eV~50 keV 温度范围内,计算了n = 4~18 的DR速率系数,并外推到了n= 100,得到总DR 速率系数。比较总DR 速率系数、三体复合(TBR) 以及辐射复合(RR) 速率系数,结果表明DR 速率系数在研究的温度范围内远大于TBR 和RR 速率系数,其将明显地影响ITER 等离子体的电离平衡和离化态布居。Based on the fully relativistic configuration interaction method, theoretical calculations are carried out to research the dielectronic recombination (DR) processes, in which W44+ ions in the ground state 3s23p63d104s2 trap an electron to form doubly excited states (3s23p63d104s2)nln’l’(n =4~6,n′= 4~7). The comparison of the DR rate coefficients of different shells shows that DR approach is as follow: the 4s subshell excitation dominates to DR at low temperature, but 3d subshell excitation attributes to DR at high temperature. Total DR rate coefficients from n=4~18 are evaluated directly, and the results are extrapolated up to n = 100 in the temperature range from 1 to 5×104 eV, and thus get the total DR rate coefficients. Compared total DR rate coefficients to three-body recombination (TBR) rate coefficients and radiative recombination (RR) rate coefficients, it showed that the total DR rate coefficients obviously significantly greater than other two recombination rate coefficients, and thus it obviously influence ionization equilibrium and ionization state population of ITER plasma.     

基于双激发态对稠密等离子体中双电子复合速率系数的研究

讨论了稠密等离子体中双电子复合速率系数的计算方法,推导出了在双激发态间跃迁过程和关于双激发态的碰撞电离和自电离过程的影响下双电子复合速率系数作为关于电子密度函数的计算公式,并以类氖镍离子为例进行了计算.计算结果展示了双电子复合速率系数随电子密度增大的具体变化趋势.此外,还给出了在不同原子过程影响下双电子复合速率系数的数据,并进行了分析.     

Dielectronic Recombination Rate Coefficients for Nickel-like Ytterbium

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Enhanced nonlinear double excitation of He in intense extreme ultraviolet laser fields

Nonlinear, three-photon double excitation of He in intense extreme ultraviolet free-electron laser fields (～24.1 eV, ～5 TW/cm2) is presented. Resonances to the doubly excited states converging to the He+ N=3 level are revealed by the shot-by-shot photoelectron spectroscopy and identified by theoretical calculations based on the time-dependent Schr?dinger equation for the two-electron atom under a laser field. It is shown that the three-photon double excitation is enhanced by intermediate Rydberg states below the first ionization threshold, giving a greater contribution to the photoionization yields than the two-photon process by more than 1 order of magnitude.     

Kinematically complete study of dissociative ionization of by ion impact

We present a kinematically complete study of dissociative ionization of D(2) by 13.6 MeV/u S(15+) ions. The experiment allows us to unravel the competing mechanisms, namely, direct single ionization, autoionization of doubly excited states, ionization excitation, and double ionization, and to analyze the corresponding electron angular distribution from fixed-in-space molecules. The conclusions are supported by theoretical calculations in which the correlated motion of all electrons and nuclei and the interferences between them are described from first principles.     

Double-well states of ungerade symmetry in H2: first observation and comparison with Ab initio calculations

The observation of a new class of long-lived outer well states of ungerade symmetry (B"B1Sigma+u) in molecular hydrogen, lying above the ionization threshold, is reported. Rovibrational levels within a potential extended over internuclear separations of R = 7-25 a.u. are experimentally investigated in a triple resonance scheme. Good agreement ( <0.5 cm(-1)) with updated ab initio calculations is found for vibrational levels up to v = 26, demonstrating that such calculations can now be extended to this energetic range above ionization, as long as interaction with the Rydberg manifolds is shielded by a barrier. The dynamical behavior (predissociation and autoionization) of this class of " u" symmetry states is remarkably different from similar outer well states of " g" symmetry; this phenomenon can be understood from the structure of doubly excited electronic states.     

激发态之间的电离与复合过程对类氖锗19.6nm X射线激光增益系数的影响

考察了激发态之间的电离与复合过程对等离子体状态的影响,并对其原因进行了细致的分析,分别考察了对1.0ns,100ps和5ps激光驱动的类氖锗19.6nm Ｘ射线激光增益系数的影响.研究表明,对于5ps激光驱动的瞬态机理X射线激光来讲,因增益区处在高密度区,所以,激发态之间的电离与复合过程对X射线激光将不可以忽略.对于1.0ns和100ps激光驱动的亚稳态机理X射线激光来讲,在电子密度小于等于5×10²⁰cm^－3的区域,忽略激发态之间的电离与复合使增益的时间半高全 关键词： X射线激光 矩阵分块法 类氖锗 双电子激发态     

Effect of collisional transitions on the population distributions of excited atoms in a plasma

The effect of collisional transitions on the population distribution of excited atoms has been studied by considering a plasma in which the electron density varies with time. It has been found that for highly excited states, for which the ionization rate is much larger than that of electron-density variations, the collisional transitions are not important compared with the collisional ionization and recombination processes. However, for intermediate and lower excited states, they play an important role in making the population distribution approach Saha equilibrium with the electrons.     

Observation of triplet doubly excited states in single photon excitation from ground state helium

We have observed, for the first time, LS-forbidden triplet doubly excited states, in single photon excitation of ground state helium, below the second ionization threshold. These states are identified as (3)D(o) and (3)P(o) and their excitation is due to spin-orbit interaction that mixes them with the optically allowed (1)P(o) states. This observation is possible due to the very high efficiency in detecting metastable atoms created after the fluorescence decay of the doubly excited states, and the new capabilities of third generation synchrotron vacuum ultraviolet sources with high resolution beam lines.     

Electronic Structure of Helium Atom in a Quantum Dot

Bound and resonance states of helium atom have been investigated inside a quantum dot by using explicitly correlated Hylleraas type basis set within the framework of stabilization method.To be specific,precise energy eigenvalues of bound 1sns(~1S~e)(n=1-6)states and the resonance parameters i.e.positions and widths of~lS~e states due to 2sns(n=2-5)and 2pnp(n=2-5)configurations of confined helium below N=2 ionization threshold of He~+have been estimated.The two-parameter(Depth and Width)finite oscillator potential is used to represent the confining potential due to the quantum dot.It has been explicitly demonstrated that the electronic structural properties become sensitive functions of the dot size.It is observed from the calculations of ionization potential that the stability of an impurity ion within a quantum dot may be manipulated by varying the confinement parameters.A possibility of controlling the autoionization lifetime of doubly excited states of two-electron ions by tuning the width of the quantum cavity is also discussed here.     

Low-frequency strong-field ionization and excitation of hydrogen atom

The dynamics of hydrogen atom in the presence of a strong radiation field of the titanium-sapphire laser is studied for the Keldysh parameters γ ≥ 1 and γ ≤ 1. It is demonstrated that the ionization is supplemented with the effective population of the excited states with the principal quantum numbers n = 5–10 in the entire range of variation in the Keldysh parameter. The population of the excited Rydberg states can be interpreted as a consequence of the multiphoton resonance involving the initial 1s state and a group of excited states in the vicinity of the continuum boundary with the simultaneous repopulation of these states by Λ-type Raman transitions under the action of the laser field. The resulting coherent Rydberg packet appears to be stable with respect to ionization, so that the ionization of the atomic system in the presence of strong electromagnetic field is suppressed. Physical reasons for the stabilization are discussed. An interpretation of the effective population of the Rydberg states in the recent experiments on the ionization of atomic helium by the titanium-sapphire laser is proposed.     

CII的光电离截面的理论计算

 使用R-矩阵方法,对CII基态的光电离截面进行了六态和十态的密耦计算,得到了入射光子能量从1.8Ry到4.3Ry的总光电离截面,长度与速度表示符合很好。计算得到的截面包含了复杂的共振结构。与由英法等国联合开展的不透明度工程的理论计算结果进行了比较,两者在电离阈附近符合得比较好。计算表明,收敛于较高电离阈的共振系列对收敛于较低电离阈的共振系列有较大的干扰。由分波和电离后处于特定靶态的光电离共振峰的位置可确定CII单双高激发态能级的位置。     

Au激光等离子体的双电子复合速率系数

基于准相对论多组态HartreeFock理论和扭曲波近似,采用组态平均的方法,从头计算了类铁金离子类镓金离子的双电子复合速率系数,计算中包含了大量稠密的自电离能级,由于宽广的自电离能级分布和极其复杂的级联效应,造成高Z材料Au的双电子复合速率系数不同于低Z元素的特征,与现有文献的类镍金离子比较,结果表明,在“神光Ⅱ”实验装置诊断的电子温度约为2keV,电子密度约为6×1021cm-3,Au激光等离子体不同理论之间的双电子复合速率系数误差不到10%.这对于使用超组态碰撞辐射模型模拟Au的激光等离子体M带细致 关键词： 双电子复合 类铁金离子类镓金离子 复合速率系数     

Inelastic electron collisions with Rydberg atoms

The standard classical method of computer simulation is used for evaluation of the inelastic cross section in electron collisions with a highly excited (Rydberg) atom. In the course of collision, the incident and bound electrons move along classical trajectories in the Coulomb field of the nucleus, and the scattering parameters are averaged over many initial conditions. The reduced ionization cross section of a Rydberg atom by electron impact approximately corresponds to that of atoms in the ground states with valence s-electrons and coincides with the results of the previous Monte Carlo calculations. The cross section of an atom transition between Rydberg atom states as a result of electron impact is used for finding the stepwise ionization rate constant of atoms in collisions with electrons or the rate constant of three-body electron-ion recombination in a dense ionized gas because these processes are determined by kinetics of highly excited atom states. Surprisingly, the low-temperature limit of electron temperatures is realized when the electron thermal energy is lower than the atom ionization potential by about three orders of magnitude, as follows from the kinetics of excited atom states. The article is published in the original.     

Ca和Sr原子n′dnl自电离态在低电场中的线性Stark效应

用激光多步激发技术观察了Ca和Sr原子n′dnl双电子激发自电离态的电场效应。Stark光谱显示,在F<1/3n⁵的低电场中,Stark能级分裂与外电场强度线性相关。也观察了近简并l亚能级的Stark混合使自电离共振谱线在外电场中的增宽。这一效应在高温等离子体中对双电子复合速率的增加起重要作用。 关键词：     

Autoionization of triply excited rydberg series

The Auger rates of triply excited Rydberg series are shown to behave rather differently from doubly excited series. It is shown that in hollow atoms the Auger decay rates for Rydberg series of the type 2l2l(')nl(") with n>/=2 are expected to be nearly independent of n, while for doubly excited series of the type 2lnl(') the decay rate in general decreases with increasing n. In addition the ratio between the rates for 2l2l(')nl(") Rydberg series with different l(") values will be fixed and often the ratio will be equal to one.     

辐射输运实验中的Al等离子体发射光谱研究

SGII装置上用八路激光注入金腔产生高温辐射源,然后利用该辐射源来加热输运腔中的掺Al泡沫样品.从测量得到的Al类氦离子发射光谱可以观察到a—d,qr伴线的强度明显高于jkl伴线的强度,由此可以确定出光子激发和电离过程对输运腔中等离子体的形成不可忽略.除此之外,还观察到较强的互组合线发射,这表明存在一个低密度区域.最后考虑到实验测量得到的Al类氦离子发射光谱是时间、空间积分,利用两个状态等离子体的发射光谱合成再现了实验光谱. 关键词： 发射光谱 辐射加热 光谱诊断     

Kinetics of Rb<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> and Rb<Superscript>+</Superscript> formation in laser-excited rubidium vapor

We have studied the formation of the molecular ion Rb₂⁺ and the atomic ion Rb⁺. These are created in laser excited rubidium vapor at the first resonance, 5s–5p and 5p-nl transitions. A theoretical model is applied to this interaction to explain the time evolution and the laser-power dependence of the population density of Rb⁺ and Rb₂⁺. A set of rate equations which describe: the temporal variation of the population density of the excited states; the atomic ion density; and the electron density, were solved numerically under the experimental conditions of Barbier and Cheret. In their experiment the Rb concentration was 1×10¹³cm⁻³ and the laser power was taken to be 50–500 mW at vapor temperature = 450 K. The results showed that the main processes for producing Rb₂⁺ are associative ionization and Hornbeck-Molnar ionization. The calculations have also showed that, the atomic ions Rb⁺ are formed through the Penning Ionization (PI) and photoionization processes. Moreover, a reasonable agreement between the experimental results and our calculations for the ion currents of the Rb⁺ and Rb₂⁺ is obtained.