用于研究铝等离子体软X射线光谱的碰撞-辐射模型

我们建立了一个以AlXI和AlXII离子为主的碰撞一辐射模型,模型中考虑了碰撞电离和复合,碰撞激发和退激发,辐射复合和自发辐射跃迁等原子过程.本文还分析了该模型的计算结果,包括离子丰度分布,辐射损失,及诊断的特性.     

类Li氧等离子体光谱模拟

 在FAC程序包中碰撞辐射模型的基础上,模拟出了L壳层的类Li氧等离子体的X射线辐射光谱,其中包括了单、双和三离子模型。经过分析得出,除了碰撞激发以外,级联效应和其它的动力学过程(如：碰撞电离、双电子复合、辐射复合以及共振激发等)对光谱的贡献都是不能被忽略的。并分析了类Li氧等离子体各动力学过程与温度和光谱相对强度之间的关系,分析结果表明X射线光谱的强度能及时响应等离子体温度的变化。     

Au等离子体M带5f-3d跃迁的电子离子碰撞激发速率系数

电子离子碰撞激发速率系数在超组态碰撞辐射模型中真实模拟非局域热动力学平衡Au激光等离子体M带谱 5f 3d跃迁中各种复杂电荷态离子的电离态特性 (譬如离子的平均电离度 ,相对丰度和能级布居数 )是必不可少的。基于准相对论多组态Hartree Fock方法和扭曲波玻恩交换近似 ,采用自编的扭曲波程序ACDW (9)和Fit(9) ,从头计算了Au等离子体M带 5f 3d电子离子碰撞激发速率系数。结果表明 :在“神光II”实验装置诊断的电子温度约 2keV ,电子密度约 6× 10 2 1cm-3 范围内 ,这些电子离子碰撞激发参数有利于采用超组态碰撞辐射模型模拟Au的激光等离子体M带 5f～ 3d细致谱的平均电离度和电荷态分布。     

高Z等离子体中的双电子复合与电子碰撞激发

 采用准相对论性Hartree-Fock-Relativistic方法与不可分辨跃迁组模型相结合,对Au和Ta元素的类Ni离子的双电子复合速率,以及Au元素类Cu离子的电子碰撞激发速率进行了计算。计算结果表明,对于Au类Ni离子的3d¹⁰-3d⁹4l5f-3d¹⁰4l双电子复合过程以及类Cu离子的3d¹⁰4l-3d⁹4l5f电子碰撞激发过程,当电子温度高于1.0 keV时,电子离子碰撞激发速率随电子温度增加而增加,双电子复合速率随电子温度增加而减小,并且电子碰撞激发对谱线辐射的贡献要比双电子复合大得多。     

Li-like镁等离子体X射线光谱模拟

利用碰撞辐射平衡和离化平衡下的等离子体X射线发射谱理论,对镁元素等离子体在中低电子密度、中高电子温度范围内,以碰撞激发、共振激发、离化、辐射复合和双电子复合等动力学过程为主的Mg10 、Mg9 和Mg8 三离子体系X射线谱进行了理论模拟,得到其X射线光谱,反映出X射线辐射谱波长、强度同电子温度之间的关系,得到了等离子体诊断所关心的电子温度的定性关系.     

类氖氙离子LMn双电子复合模拟谱

在双电子复合过程发生的能量范围内,发射X光子的原子过程除双电子复合过程外还有辐射复合、共振激发、共振复合以及直接激发原子过程.本文使用相对论组态相互作用方法计算了这些过程的截面,比较了在双电子复合过程发生的能量范围内这些原子过程的截面与双电子复合过程截面,探讨了这些过程对双电子复合过程的影响.研究结果表明,辐射复合截面随入射电子束能量的增大迅速减小,在双电子复合能量范围内几乎为一常数,可以作为本底来处理;共振激发和共振复合过程对双电子复合过程的影响可以忽略不计;当入射电子束能量高于靶离子的第一激发能时,电子碰撞直接激发截面与高Rydberg态的截面连成一片,随着入射电子束能量的增加,电子碰撞直接激发截面越来越大,这时必须考虑直接激发过程.使用相对论组态相互作用方法计算了类氖氙离子的双电子复合截面,其结果与已有的部分实验和理论结果很吻合.     

类氖氙离子LMn双电子复合模拟谱

在双电子复合过程发生的能量范围内,发射X光子的原子过程除双电子复合过程外还有辐射复合、共振激发、共振复合以及直接激发原子过程. 本文使用相对论组态相互作用方法计算了这些过程的截面,比较了在双电子复合过程发生的能量范围内这些原子过程的截面与双电子复合过程截面,探讨了这些过程对双电子复合过程的影响. 研究结果表明,辐射复合截面随入射电子束能量的增大迅速减小,在双电子复合能量范围内几乎为一常数,可以作为本底来处理;共振激发和共振复合过程对双电子复合过程的影响可以忽略不计;当入射电子束能量高于靶离子的第一激发能时,电子碰撞直接激发截面与高Rydberg态的截面连成一片,随着入射电子束能量的增加,电子碰撞直接激发截面越来越大,这时必须考虑直接激发过程. 使用相对论组态相互作用方法计算了类氖氙离子的双电子复合截面,其结果与已有的部分实验和理论结果很吻合.     

单、双洞态镁离子的退激发及末电离态离子分布的研究

在分析双洞相关退激发对双洞态退激发的贡献较小的基础上，依据辐射-俄歇-双俄歇级联退激发模型(RACDA)研究了Mg¹⁺(1s^-1)（K壳层单洞态镁离子）和Mg²⁺(1s^-2)（K壳层双洞态镁离子）的退激发过程，计算了它们的末电离态离子的分布，并与辐射-俄歇级联退激发模型的结果进行了比较.RACDA模型计算的Mg¹⁺(1s^-1)的4价末电离态离子的相对丰度较大，而辐射-俄歇级联退激发模型(RAC)的结果中就没有出现4价离子；两种模型计算Mg²⁺(1s^-2)的6价末电离态离子的丰度非常大，而RAC模型下的Mg²⁺(1s^-2)退激发后不产生6价离子. 关键词： 双洞态退激发 RACDA退激发模型     

碰撞辐射稳态等离子体电荷态分布的一种扩展模型

通过等离子体中离子激发-退激发平衡关系,构造一种离子激发组态之间满足的非Boltzmann分布,利用这个分布作为权函数对原子过程速率系数进行平均,构造出一个扩展的碰撞辐射稳态模型.利用该模型计算从低Z到高Z元素等离子体平均离子电荷随电子温度的变化.进而研究非Boltzmann分布对平均电离度和激发组态相对密度的影响.结果表明,它对相对激发组态密度的影响非常显著. 关键词： 扩展的碰撞辐射稳态 概率分布 能级动理学     

Auq+(q=53-47)激光等离子体的辐射复合速率系数

辐射复合过程在超组态碰撞辐射（SCROLL）模型中真实模拟非局域热动力学平衡（non-LTE）高Z材料Au激光等离子体M带谱5f-3d跃迁中各种复杂离子的电离态特性是一个主要过程。基于准相对论多组态Hartree-Fock理论和扭曲波近似,采用组态平均的方法,从头计算了金M带类铁金离子-类锗金离子的辐射复合速率系数,计算过程中包含了大量的单激发和双激发态,结果表明高Z元素由于自电离能级的广泛分布和复杂的级联效应,致使高Z元素的辐射复合系数不同于低Z元素的,其计算结果可用来模拟Au的激光等离子体M带5f-3d跃迁的平均电离度和电荷态分布及能级布居数。     

Radiative energy losses from low and moderate Z elements

Radiative energy losses from twelve low and moderate Z elements are calculated for temperatures ranging from 2 eV to 20 keV. Each element is assumed to be in coronal equilibrium, so that the ionization structure is determined by balancing collisional ionization and autoionization against radiative and dielectronic recombination. The radiative losses are calculated by adding the emission due to bremsstrahlung, radiative and dielectronic recombination, 2-photon processes, and line radiation. Polynomial fits to the loss rates, suitable for use in computer programs, are given for each element.     

Spectrum Simulation of Li-Like Aluminium Plasma

X-ray emission spectra for L-shell of Li-like aluminium ions are simulated by using the flexible atomic code based on the collisional radiative model. Atomic processes including radiative recombination, dielectronic recombination, collisional ionization and resonance excitation from the neighbouring ion （Al^9＋ and Al^11＋ ） charge states of the target ion （Al^10＋） are considered in the model. In addition, the contributions of different atomic processes to the x-ray spectrum are analysed. The results show that dielectronic recombination, radiative recombination, collisional ionization and resonance excitation, other than direct collisional excitation, are very important processes.     

Effect of dielectronic recombination on the charge-state distribution and soft X-ray line intensity of laser-produced carbon plasma

The effect of dielectronic recombination in determining charge-state distribution and radiative emission from a laser-produced carbon plasma has been investigated in the collisional radiative ionization equilibrium. It is observed that the relative abundances of different ions in the plasma, and soft X-ray emission intensity get significantly altered when dielectronic recombination is included. Theoretical estimates of the relative population of CVI to CV ions and ratio of line intensity emitted from them for two representative formulations of dielectronic recombination are presented.     

Intense laser-cluster interaction in the strong coupling regime

The interaction of noble gas clusters with moderately intense laser radiation at 100 and 800 nm is investigated via molecular dynamics simulations. It is shown that the laser-cluster interaction creates a strongly coupled plasma, which is characterized by a dominance of collisional processes. This has led to several findings. (1) A new heating mechanism is identified that explains the observation of unusually high-charge states in recent experiments with 100 nm radiation at DESY. We find that energy absorption takes place in the following cycle: many-body collisions resulting in an enhanced recombination of free electrons to exited states, and subsequent reionization. (2) Cluster interaction with 800 nm radiation is a promising system for investigating the transition from weakly coupled plasmas, where collective processes dominate, to strongly coupled plasmas. We achieve this transition by varying a single parameter: the laser intensity. The experimental and theoretical accessibility of laser-cluster interaction, thus, allows a systematic combined study of the interplay between collective and collisional processes.     

Collisional recombination in nonideal plasmas

We suggest a model that allows one to consider the kinetics of collisional recombination in a nonideal plasma and to calculate its rate by the molecular dynamics method. We have found that the dependence of the collisional recombination rate on the plasma coupling parameter differs significantly from the extrapolation of the three-body recombination rate to the nonideal region. The recombination rate in a strongly coupled plasma has been found to decrease with increasing coupling parameter. We have established that the effect of plasma nonideality increases with ion charge. The recombination kinetics is shown to depend significantly on how the ions are arranged in the medium. Collisional recombination transforms into three-body one as the coupling parameter of the medium decreases.     

Oxygen impurity radiation from Tokamak-like plasmas

We have constructed a nonhydrodynamic coronal model for calculating radiation from impurity atoms in a heated plasma. Some recent developments in the calculation of dielectronic recombination rate coefficients and collisional excitation rate coefficients are included. The model is applied to oxygen impurity radiation during the first few milliseconds of a TFR Tokomak plasma discharge, and good agreement with experimental results is obtained. Estimates of total line and continuum radiation from the oxygen impurity are given. It is shown that impurity radiation represents a considerable energy loss.     

Elastic state of stress in narrow-gap semiconductors: A fundamental possibility to increase the quantum yield of infrared radiation

In a narrow-gap semiconductor with a direct band gap, an elastic state of stress provides the possibility to considerably reduce the collisional interband recombination because of the transformation of the valence band. As a result, the quantum yield of infrared radiation in the interband transition region increases drastically. The experimental results are obtained for InSb crystals.