Measurement and analysis of the extreme ultraviolet emission band of laser-produced antimony plasmas

The temporal evolution of extreme ultraviolet (EUV) emission spectra of laser-produced antimony (Sb) plasmas has been measured in the 7–16 nm wavelength region using spatio- temporally resolved lase-produced plasma spectroscopy technique. The spectral profiles involve an intense quasi-continuous band with superimposed intense characteristic radiation and are different with the increase of delay time. The spectral structures were also analyzed according to Hartree–Fock calculations with configuration interaction effects and contributed from 4d–4f, 4d–4p, and 4d–5f unresolved transition arrays of Sb⁷⁺ – Sb¹³⁺. A steady-state collisional- radiative model was used to estimate the electron temperature and density range of Sb plasmas. This work would enrich the spectral data of highly-charged ions and provided a possible selection for developing EUV light sources.     

蚊香元素成分的LIBS检测分析

激光诱导击穿光谱(LIBS)作为一项很有前景的元素分析技术,具有原位测量、远程监控等优势,而对蚊香样品的LIBS检测应用是一项较新的课题。为将LIBS技术实际应用于环境监测领域,实验中利用时间分辨的激光诱导击穿光谱技术对蚊香样品的激光等离子体光谱进行了测量和分析,确定出蚊香中Al、Mn、Mg、Sr、Zn、Ba、Na、Ca、Fe、Si和H的11种元素成分;基于等离子体局域热动力学平衡模型,计算了等离子体温度。利用自由定标分析方法计算了上述元素的相对含量。实验结果表明激光诱导击穿光谱技术可以用于有害元素的快捷有效检测。     

Improved sensitivity on detection of Cu and Cr in liquids using glow discharge technology assisted with LIBS

Laser-induced breakdown spectroscopy-assisted glow discharge (LIBS-GD) for analysis of elements in liquid was proposed, and it was applied to detect heavy metals in highly sensitive mixed solutions of Cu and Cr. During the experiments of GD and LIBS-GD, the experimental parameters have been optimized and the optimal voltage is 450 V, laser energy is 60 mJ, and the delay time is 4000 ns. Furthermore, the calibration curves of Cu and Cr under GD and LIBS-GD experiments have been established, and the limits of detection (LODs) of Cu and Cr were obtained with the method of GD and LIBS-GD, respectively. The LOD of Cu decreased from 3.37 (GD) to 0.16 mg l⁻¹ (LIBS-GD), and Cr decreased from 3.15 to 0.34 mg l⁻¹. The results prove that the capability of elemental detection under LIBS-GD has improved compared with the GD method. Therefore, LIBS-GD is expected to be developed into a highly sensitive method for sewage detection.     

离焦量对空气中YAG激光诱导Cu等离子体空间特性的影响

利用Nd:YAG脉冲激光在空气中烧蚀Cu靶,产生激光等离子体羽,通过改变离焦量获得相应的等离子体的空间谱;用光谱学方法分析了三种离焦量下空间谱线结构和空间等离子体的电子温度演化规律;并对等离子体光谱的特性和产生机制进行了讨论.结果表明:离焦量对等离子体的谱线强度、谱线结构、电子温度的空间特性都有影响,特征谱强度最大值出现在空间位置1.0mm附近,离焦量为-2mm时电子温度最高.     

激光诱导Al等离子体中电子密度的实验研究

用Nd:YAG脉冲激光器产生的1.06μm激光,在低压环境下烧蚀金属Al靶获得等离子体,并观测其空间分辨发射光谱;利用AlⅠ的两条发射谱线的Stark展宽计算了Al等离子体电子密度,研究了电子密度随空间的演化规律。结果发现:在靶面附近电子密度达到最大值,随着离靶面距离的增加,电子密度逐渐减小,从微观物理机制的分析推断:激光诱导等离子体的复合辐射是电子密度减少的主要原因。另外,还探讨了激光能量的变化对等离子体电子密度的影响。     

激光诱导Cu等离子体光谱的空间特性研究

利用Q -开关Nd :YAG激光器产生的 1.0 6 μm、10ns的脉冲激光聚焦在空气中的Cu靶上 ,观测了激光诱导的Cu等离子体发射光谱。采用激光能量为 4 5mJ/ pulse ,分析了波长范围为 4 4 0nm到 5 4 0nm的空间分辨发射光谱。在局部热力学平衡 (LTE)条件近似下 ,根据谱线的相对强度 ,得到了等离子体电子温度约在 10 4K以上 ,给出了靶面附近电子温度和谱线半高全宽的空间演化规律。     

Dielectronic Recombination of Br-Like Tungsten Ions

Accurate data for dielectronic recombination of tungsten ions are essential in the modeling of tungsten impurity transport and radiative power loss in International Thermonuclear Experimental Reactor （ITER）. Theoretical calculations have been made for dielectronic recombi- nation （DR） rate coefficients of Br-like tungsten ions using a flexible relativistic atomic code （FAC） from i eV to 50 keV. Level-by-level calculations are carried out for evaluating the contributions to DR through all the relevant Kr-like tungsten ions autoionizing inner-shell excited configuration complexes： （3s23p63d10）-14s24p5nlntl＇ （n = 4-5, n＇ = 4-100,l＇ = 0-8）, （4s24pS）-lnln＇l＇ （n = 4-6, n＇ = 4-100, l＇ = 0-12）. Comparison of the rate coefficients for 3s, 3p, 3d, 4s and 4p subshell excitations shows that the 4p subshell excitation dominates over the whole temperature region, 4s subshell excitation at low temperature and 3p, 3d subshell excitations at high temperature can not be neglected. In order to facilitate simple applications, the total DR rate coefficient, △n = 0,1 and 2 core excitations DR rate coefficients are fitted to an empirical formula.     

LIBS Detection of Heavy Metal Elements in Liquid Solutions by Using Wood Pellet as Sample Matrix

Laser-induced breakdown spectroscopy （LIBS） has been applied to the analysis of heavy metals in liquid samples. A new approach was presented to lower the limit of detection （LOD） and minimize the sample matrix effects, in which dried wood pellets absorbed the given amounts of Cr standard solutions and then were baked because they have stronger and rapid absorption properties for liquid samples as well as simple elemental compositions. In this work, we have taken a typical heavy metal Cr element as an example, and investigated the spectral feasibility of Cr solutions and dried wood pellets before and after absorbing Cr solutions at the same experimental conditions. The results were demonstrated to successfully produce a superior analytical response for heavy metal elements by using wood pellet as sample matrix according to the obtained LOD of 0.07 ppm for Cr element in solutions.     

Effect of dielectronic recombination on charge-state distribution in laser-produced plasma based on steady-state collisional-radiative models

Armed with four different steady-state collisional-radiative (CR) models, we investigated the effect of dielectronic recombination (DR) on the charge-state distribution in laser-produced silicon plasma. To assess this effect, we performed a series of temporally resolved spectra of highly charged Si ions in the extreme ultraviolet region. Ab initio calculations of the DR rate coefficients were done for Si⁶⁺–Si⁴⁺ ions. We also analyzed the evolution of the collisional ionization, radiative recombination, three-body recombination, photo-ionization, and DR rate coefficients as a function of electron temperature. The electron temperature and electron density for different delay times were obtained by comparing the normalized experimental and simulated spectra. The ion fraction and average charge state from the four different CR models were also obtained. The results indicate that the DR process has a greater influence in the stage of plasma evolution that cannot be neglected in plasma diagnoses.