不同微场分布函数下的光谱线型

根据光谱学,总的光谱线型是各种加宽机制的卷积结果。考虑到等离子体中的离子碰撞,Stark加宽本质上是一种非对称的光谱线型, 其中微场分布函数对光谱线型起着非常关键的作用。该文利用不同的微场分布函数研究了微场分布函数对总的光谱线型的影响。研究结果表明,在电子加宽参数和离子加宽参数很小时,不同微场分布函数对整个光谱线型的影响基本相似,但随着离子加宽参数的增加,3种不同的微场分布函数对Stark光谱线型的影响逐渐增加; 随着电子加宽参数的增加,不同的微场分布函数对Stark光谱线型的影响也逐渐增加; 但总体上Holtsmark分布和Nearest-Neighbor场分布下的光谱线型差别较小,但是Mayer模型对光谱线型影响较大。特别是,当离子加宽参数较大时,Mayer模型对光谱线型的影响异常明显,这也正说明离子间碰撞剧烈时对光谱线型的影响很大。该结果对等离子体参数诊断有一定参考价值。     

不同微场分布函数对Stark线型的影响

利用不同的微场分布函数研究了其对Stark加宽光谱线型的影响.根据Stark加宽理论,考虑到等离子体中的离子碰撞,Stark加宽本质上是一种非对称的光谱线型,其中微场分布函数对光谱线型起着非常关键的作用.研究结果表明,总体上Holtsmark分布和Nearest-Neighbor场分布下的Stark光谱线型差别不太大,但是Mayer模型对Stark加宽光谱线型影响较大.并且随着离子加宽参数的减小,三种不同的微场分布函数对Stark光谱线型的影响逐渐减小;随着电子加宽参数的减小,不同的微场分布函数对Stark光谱线型的影响也逐渐减小;同时发现,当离子加宽参数减小到一定程度时,不同微场分布函数对整个光谱线型的影响基本相似,这也正说明离子间碰撞剧烈时对光谱线型的影响很大.     

Stark线形与ICF等离子体诊断

本文理论计算了ICF等离子体中离子或原子的发射谱线线形函数,该线形主要是由Stark效应产生的.我们的研究表明该谱线线形函数的宽度随电子温度变化很缓慢,而随电子密度变化很敏感.结合局部热动平衡理论,并利用实验测量的氩(Ar)和硫(S)的α线与β线的线强比,分别估算出等离子体的电子温度为885 eV和793 eV.通过理论计算的Stark线形函数与ICF实验谱线的比较,估算出ICF等离子体的电子密度Ne=1.0×1024.     

SiH4激光等离子体内H谱线的线型研究

本工作利用光学多道分析仪(OMA Ⅲ)测量了脉冲TEA CO₂激光诱发的SiH₄等离子体内H Balmer系的H_α,H_σ和H_γ线的线型。结果表明,三条谱线的FWHM(半值全宽度)随跃迁上能级的主量子数的增加而增加,即△λ_1/2(H_α)<△λ_1/2(H_β)<△λ_1/2(H_γ)。通过对等离子体内各类加宽机制的讨论,得出等离子体内谱线的主要加宽机制为Stark加宽。由H_α线的实验线型与Stark加宽理论线型的拟合,得到等离子体的两个重要参量,平均电子密度N≈10¹⁷cm^-3,电子温度T≈40 000K。由H_β线的时间分辨测量得到等离子体的电子密度随时间的演变曲线。 关键词：     

发射光谱法对早期激光诱导铝合金等离子体诊断研究

对激光诱导等离子体参数进行诊断有多种方法,其中采用发射光谱法对其诊断是一种重要的方法。文中采用Nd∶YAG固态激光器,输出波长1 064 nm红外激光与铝合金样品相互作用,深入研究了铝合金等离子体产生早期(<1 μs)谱线轮廓、谱线强度、线背比、谱线半峰宽及位移等随时间演变规律。研究表明,激光与物质相互作用早期,电子数密度非常大,电子与离子及原子之间的相互作用非常强烈,谱线的Stark展宽效应非常明显,导致多重谱线重叠在一起,随时间演变,电子数密度及电子温度的降低,多重谱线的半峰宽越来越窄且谱线轮廓对称性越来越好。MgⅠ285.212 6 nm谱线强度早期逐渐增强,大约100 ns左右谱线强度达到最大值,然后谱线强度呈逐渐减小的趋势,这是由于等离子体产生早期,电子及离子占主导地位,故早期原子谱线强度较弱,随时间演变,电子与离子之间的复合,原子数密度逐渐增加,故原子谱线逐渐增强,达到最大值之后,由于等离子体激发温度的降低,故谱线强度逐渐减弱。以NIST波长位置为参考,等离子体产生的早期谱线发生了红移,连续背景强度随时间演变呈幂函数形式急剧递减,与之相反,谱线的连续背景强度与谱线强度相比,连续背景衰减的速度更为迅速,故导致谱线信背比随时间演变呈增大趋势,本研究对等离子体早期这些现象从理论角度进行了深入探讨。     

相对论热等离子体中电子声波的非线性频移

研究了相对论电磁波在热等离子体中传播时的色散特性以及由于非线性电子声波激发引起的电子声波的非线性频移。基于相对论激光在热等离子体中传播的电磁流体物理模型,采用流体的非线性频移理论,利用微扰法得到了描述相对论激光与热等离子体相互作用时谐波产生的非线性频移方程。结果表明,等离子体密度、电子温度和一阶谐波振幅是决定相对论热等离子体中非线性频移的主要因素。在弱激发下,非线性频移随着电子温度和一阶谐波振幅的增大而增大,等离子体密度抑制非线性频移。电子声波非线性频移对等离子体密度和电子温度的依赖表现出了强烈的非线性特征。研究结果为深入理解高能量激光与热等离子体相互作用中谐波的产生及引起的非线性频移提供了理论依据。     

激光诱导Pb等离子体光谱的时间演化特性

用 Nd:YAG脉冲激光器产生的1.06 μm激光在空气中烧蚀金属Pb靶产生等离子体,并观测了其时间分辨的发射光谱. 依据光谱线波长、相对强度等参数估算了不同延迟时间等离子体的电子温度;由PbI线的Stark加宽计算得到等离子体的电子密度;讨论了电子温度和电子密度的时间分布特征. 电子温度平均为14500 K、电子密度达到1017 cm-3. 从等离子体产生、发展机制的角度定性探讨了电子温度和电子密度的时间分布特征.     

激光诱导Pb等离子体光谱的时间演化特性

用 Nd:YAG脉冲激光器产生的1.06 μm激光在空气中烧蚀金属Pb靶产生等离子体,并观测了其时间分辨的发射光谱. 依据光谱线波长、相对强度等参数估算了不同延迟时间等离子体的电子温度;由PbI线的Stark加宽计算得到等离子体的电子密度;讨论了电子温度和电子密度的时间分布特征. 电子温度平均为14500 K、电子密度达到1017 cm-3. 从等离子体产生、发展机制的角度定性探讨了电子温度和电子密度的时间分布特征.     

Stark效应对J-C模型腔场谱的影响

研究了计及Stark效应的J-C模型的腔场谱,通过求解本征方程导出了腔场谱的计算公式,给出了腔场处于光子数态时的数值结果,讨论了Stark效应和初始场强对标准J-C模型腔场谱的影响.发现在初始场为真空场时,两个Rabi峰的高度相等,随着Stark位移参数的增大,两峰都向低频方向移动,且频差逐渐增大;在初始场较强的情况下,Stark移动参数增大时会导致双峰的对称性消失,通过测量两峰的相对高度也可确定Stark位移参数的大小;在Stark效应较强初始场递增的情况下两峰仍向左移,但峰间距越来越小;在弱场情况下,Stark效应使两峰呈现左高右低或左低右高的峰结构.总之,改变Stark位移参数β1、β2的大小以及初始场强的强弱,可得到不同的谱线结构.     

等离子体密度对放电等离子体极紫外光源影响研究

等离子体状态是决定极紫外光源功率和转换效率的最重要因素之一,理论和实验研究上Xe气流量对放电等离子体极紫外光源辐射谱和等离子体状态的影响,对于优化光源工作条件具有重要的意义。理论上,采用碰撞-辐射模型,模拟了非局部热力学平衡条件下,不同电离度的离子丰度分布随电子温度和离子密度的变化。推导了Xe8+~Xe11+离子4d-5p跃迁谱线强度随电子温度的变化趋势。实验上,采用毛细管放电机制,利用罗兰圆谱仪测量和分析了不同等离子体密度条件下,放电等离子体极紫外光谱的变化,分析了Xe气流量对等离子体状态的影响。理论和实验结果表明： 相同的电流条件下,等离子体箍缩时的平均电子温度随着Xe气流量的增加而降低。对于4d-5p跃迁,低电离度离子与高电离度离子谱线强度的比值随着温度的增加而减少。电流28 kA、Xe气流量0.4 sccm(cm3·min-1)时,等离子体Z 箍缩平均电子温度位于29 eV附近。Xe气流量增加时,受离子密度和最佳电子温度的影响,实现Xe10+离子4d-5p跃迁13.5 nm(2%带宽)辐射谱线强度最优化的Xe气流量位于0.3~0.4 sccm之间。     

Theory of Stark broadening—II exact line profile with model microfield

A semi-classical theory of Stark broadening is presented which differs basically from current theories. No attempt is made to improve existing approximations. An exact solution is given using a model of the actual microfield incorporating all the essential information, i.e. the probability distribution and the covariance of the fluctuating microfield. Calculations can be carried out completely without approximations and no divergences are encountered. It is shown that the correct profiles are obtained in both the high- and low-density limit. Results are presented for hydrogen and helium lines.     

An analysis of Markovian model microfield methods for stark broadening

Stark broadening theories which concentrate on the statistics of the plasma electric microfield rather than the dynamics of collisions have come to be known as Model Microfield Methods. In the present paper we present an analysis of Stark broadening problems based on Markovian model microfield statistics. Our derivation permits an easy comparison with traditional Stark broadening theories such as the impact and unified theories; this comparison is used to clarify the physical nature of the approximations employed by Markovian models. The strengths and weaknesses of various models are discussed, emphasizing the kangaroo process of Brissaud and Frisch, and methods are suggested for improving the current model microfield approach.     

Electron contribution to quasistatic stark broadening

The contribution of quasistatic electrons to linear Stark broadening is evaluated by means of convolutions. A modified normalized microfield distribution including these electrons is derived. Hydrogen line profiles are calculated on this purely quasistatic basis. Comparisons with experimental results for Lyman-α and H_β yield satisfactory agreement in the line wings.     

Elementary Many‐Particle Processes in Plasma Microfields

The effect of electric and magnetic plasma microfields on elementary many‐body processes in plasmas is considered. As detected first by Inglis and Teller in 1939, the electric microfield controls several elementary processes in plasmas as transitions, line shifts and line broadening. We concentrate here on the many‐particle processes ionization, recombination, and fusion and study a wide area of plasma parameters. In the first part the state of art of investigations on microfield distributions is reviewed in brief. In the second part, various types of ionization processes are discussed with respect to the influence of electric microfields. It is demonstrated that the processes of tunnel and rescattering ionization by laser fields as well as the process of electron collisional ionization may be strongly influenced by the electric microfields in the plasma. The third part is devoted to processes of microfield action on fusion processes and the effects on three‐body recombination are investigated. It is shown that there are regions of plasma densities and temperatures, where the rate of nuclear fusion is accelerated by the electric microfields. This effect may be relevant for nuclear processes in stars. Further, fusion processes in ion clusters are studied. Finally we study in this section three‐body recombination effects and show that an electric microfield influences the three‐body electron‐ion recombination via the highly excited states. In the fourth part, the distribution of the magnetic microfield is investigated for equilibrium, nonequilibrium, and non‐uniform magnetized plasmas. We show that the field distribution in a neutral point of a non‐relativistic ideal equilibrium plasma is similar to the Holtsmark distribution for the electrical microfield. Relaxation processes in nonequilibrium plasmas may lead to additional microfields. We show that in turbulent plasmas the broadening of radiative electron transitions in atoms and ions, without change of the principle quantum number, may be due to the Zeeman effect and may exceed Doppler and Stark broadening as well. Further it is shown that for optical radiation the effect of depolarization of a linearly polarized laser beams propagating through a magnetized plasma may be rather strong. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Comments on the requirements for a general Stark broadening theory

An analysis is made of requirements for a general theory of Stark broadening applicable to both strong and weak collisions. It is pointed out in particular that inclusion of the static and weak interaction limits is not sufficient to obtain a generally valid theory. At least one other condition is necessary—a dynamic correction for strong, primarily static, collisions. The kangaroo process model microfield method is examined from this point of view, and it is shown that the model conditional probability leads to an incorrect functional form for the lowest order dynamic correction.     

GaAs半导体量子箱中电子的斯塔克效应

在有效质量近似下,利用变分法研究了在GaAs半导体量子箱中电子能量的斯塔克效应.结论表明：电场平行于量子箱的中心轴时,斯塔克能移只与量子箱高度有关;电场垂直于中心轴时,斯塔克能移仅仅与它的截面尺寸有关.当电场方向与中心轴夹角为任意角时,斯塔克能移与高度和截面都有关.同时在低场和高场极限下,理论上分析了电场大小和量箱尺寸对斯塔克能移的影响.     

GaAs半导体量子箱中电子的斯塔克效应

在有效质量近似下,利用变分法研究了在GaAs半导体量子箱中电子能量的斯塔克效应.结论表明:电场平行于量子箱的中心轴时,斯塔克能移只与量子箱高度有关;电场垂直于中心轴时,斯塔克能移仅仅与它的截面尺寸有关.当电场方向与中心轴夹角为任意角时,斯塔克能移与高度和截面都有关.同时在低场和高场极限下,理论上分析了电场大小和量箱尺寸对斯塔克能移的影响.     

Multiparametric dependence of hydrogen Stark profiles asymmetry

The Standard Theory for hydrogen spectral lines asymmetry in dense plasmas is developed on the basis of rigorous and consistent approach with respect to simultaneous and complete account of the quadrupole interaction and the quadratic Stark effect. The complex multiparametric scaling and similarity dependence of the conventional asymmetry parameter for each separate Stark component and the H_β line contour as a whole is revealed and studied in detail under the influence of: ionic microfield inhomogeneity and quadratic Stark effect in ionic microfield, electronic collision shifts and impact widths, “trivial” asymmetry sources, the Boltzmann factor and the dipole intensity scaling factor of frequency to the fourth power for the case of emission line. The comparison with the precision experiment on stabilized arc data for H_β line, important for diagnostics, is performed and analyzed from the line center up to the far line wings. An erratum to this article is available at .     

Contribution to Calculation of Ion Microfield Nonuniformity Effect on the Asymmetry of Lyman‐α Line in Dense Plasma

The high orders of Stark effects on spectral line shapes are examined in the ion‐static and electron‐impact ap‐proximations. At first the distribution functions of the spatial derivative of the ion microfield in He⁺ plasma are calculated for different plasma conditions when the coupling parameter is weak. We present new results about the spatial derivative ion microfield distributions and apply them to show the asymmetry of the Lyman‐α (Ly‐α) line in He⁺ plasma. At the second stage we show that asymmetry is affected by the spatial derivative tensor of the local ion electric field. We have used the Monte‐Carlo simulation (MCS) to compute the distribution functions for all tensor components and use them to solve the evolution equation of emitter whose solution serves to compute and therefore to show the line shape asymmetry. Good agreement of our distribution functions of ion microfield gradients and the line asymmetry with other results are obtained (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)