云地闪电通道的径向结构及光辐射特征

为揭示云地闪电通道形成和发展过程的微观物理机制,研究了云地闪电通道的径向结构及光辐射特征。利用无狭缝高速摄谱仪,在青海高原地区实施野外观测试验。在一次云地闪电中记录到了清晰可见的通道核心,而且在通道核心的外边缘和外部发光通道之间发现一个较弱的发光区。基于光谱观测结果,对比分析了首次回击和第三次继后回击的光辐射特征。实验验证了闪电通道电晕鞘模型,确定了连接点的位置,估算得到两个回击的闪击距离分别为57 m和53 m,并证实了回击放电最强的点在连接点处。由此可推断,在回击初期,云地闪电回击通道沿径向由内到外依次为通道核心-弱发光区-电晕鞘外层,即闪电通道内沿通道径向的电荷分布是不均匀的,闪电通道的光辐射特征与放电强度和持续时间密切相关。

基于LIBS-GD联用技术定量检测黄河水中Cu元素

针对目前定量检测液体中重金属元素含量方法存在的缺陷,引入了激光诱导击穿光谱-辉光放电联用(LIBS-GD)技术,并用于黄河水中铜(Cu)元素的检测。通过对不同质量浓度Cu标准溶液的测定,采用内标法建立了Cu的标准曲线,并得出Cu的检出限为0.045 mg/L。实验测量了不同采样点黄河水中Cu的质量浓度,并与火焰原子吸收光谱(AAS)方法进行了对比,结果显示,两种方法的测量结果一致性良好。LIBS-GD联用技术在Cu元素检测方面表现出良好的性能,为水体中重金属元素的检测提供了更简便高效的选择。

激光诱导击穿空气等离子体光谱及半经验理论模拟

利用Nd∶YAG激光器输出的1 064nm激光进行了激光诱导击穿空气光谱实验,测量了空气等离子体的时间分辨光谱。基于局域热动力学平衡模型,建立了模拟激光诱导击穿光谱的方法。对700~900nm波段的空气等离子体光谱进行了模拟。通过模拟结果与实验结果的比较,进一步估算出了空气中氮、氧和氩的相对含量。

Cr^(3+)胁迫对小球藻生理生化特性的影响

水体重金属污染较难处理,且会对水生物造成严重的影响。为探讨水体中重金属对藻类的毒性影响,以普通小球藻(Chlorella vulgaris)和铬(Cr^(3+))为材料,研究不同浓度Cr^(3+)对普通小球藻生理、生化特性的影响,检测不同浓度的Cr^(3+)对小球藻的毒性效应。结果表明,小球藻的最优生长温度为31℃。此条件下,Cr^(3+)浓度为3 mg·L^(-1)时,小球藻的生物量最大。Cr^(3+)的浓度低于3 mg·L^(-1)时,Cr^(3+)能促进小球藻的生长,且藻细胞中光合色素、蛋白质、可溶性糖、丙二醛(MDA)的含量及超氧化物歧化酶(SOD)的活性也逐渐增加。当各胁迫组的Cr^(3+)浓度超过3 mg·L^(-1)时,随着Cr^(3+)浓度的提高,C.vulgaris的生长受到明显的抑制,藻细胞的光合色素、蛋白质和可溶性糖含量呈现逐渐下降的趋势,而MDA含量持续增加,SOD和脯氨酸则表现出先持续增高后降低(Cr^(3+)浓度为7 mg·L^(-1)时)的趋势。证明不同浓度的Cr^(3+)对小球藻的生理生化特性有不同程度的毒性效应。

普通小球藻对不同浓度镉胁迫的生理应答

以普通小球藻(Chlorella vulgaris)为研究材料探讨不同镉浓度对小球藻生理生化特性的影响。研究结果表明:在5—40μmol/L的Cd^(2+)胁迫下,普通小球藻的蛋白质、多糖和叶绿素含量均表现为随着Cd^(2+)浓度的增加呈现逐渐增加的趋势,30μmol/L略高于对照组后又逐渐降低;小球藻细胞中SOD活性及过氧化氢(H_2O_2)含量表现出先增加后减弱的趋势,35μmol/L时达到最大;而小球藻中MDA含量随着Cd^(2+)浓度的升高一直增加。这说明在重金属镉胁迫下小球藻会通过不同的生理应答来维持自身的正常生长代谢。

液体阴极辉光放电分析溶液中的痕量铅

以铂针尖为阳极,毛细管穿入石墨碳棒且其顶端溢出的液体为阴极,构建了一种小型化的液体阴极辉光放电发射光谱(LCGD-OES)分析系统,并将其用于溶液中Pb的测定。研究了放电电压、溶液流速、电解质种类、溶液pH等对发射强度的影响,同时用Pb标准物质(GBW(E)080399)和电感耦合等离子体发射光谱(ICP-OES)对LCGD-OES的分析性能进行了评价。结果表明,最优的分析条件为:放电电压650V,pH=1.0的HNO_3为电解质,溶液流速4.5mL/min。Pb的校准曲线线性关系良好,相关系数R^2为0.9913,相对标准偏差(RSD,n=10)为0.5%,检出限为0.380mg/L,功率低于55W。本法对Pb标准物质的测试结果与标准值吻合良好,相对误差为10.0%;对实际水样的测量结果与ICP-OES的测试结果基本一致,样品回收率分别为112.43%和102.81%。以上结果表明,LCGD系统具有稳定性好、灵敏度高、精密度好、准确度高等优点,可以作为一种便携式分析仪器用于水体中Pb的直接检测。

液相辉光放电原子发射光谱法测定溶液中Cd的方法研究

通过改进放电装置,建立了一种新的液相辉光放电原子发射光谱(LGD-AES)测量溶液中Cd元素的方法。探索了放电电压和Cd浓度对放电稳定性、光谱信号强度、测定灵敏度和检出限的影响,并将测试结果与电解液阴极放电-原子发射光谱(ELCAD-AES)的分析结果进行比较。结果表明,当放电电压从600V升至720 V时,电子温度从2 000 K升至3 300 K,电子密度从2.47×10^(16)cm^(-3)降至1.77×10^(16)cm^(-3),Cd的发射光谱强度增强,灵敏度升高,检出限为1.22~2.95 mg/L。LGD-AES技术检测水中金属离子具有放电设备小型、能量消耗低、放电稳定性高、背景光谱干扰小和灵敏度高等优点。

水热法合成红色绿柱石的光谱特征研究及应用

采用常规宝石学测试方法,配合紫外可见光谱技术(UV-Vis)及傅里叶变换红外光谱技术(FTIR),对美国犹他州天然红色绿柱石及俄罗斯水热法合成红色绿柱石的宝石学特征、紫外可见吸收光谱特征、中红外光谱(MIR)特征及近红外光谱(NIR)特征进行了综合对比研究。结果表明,常规宝石学测试方法很难将上述两类宝石区别开来;紫外可见光吸收光谱对鉴定天然和合成红色绿柱石的能力很有限;同时这两种宝石的中红外吸收光谱(MIR)没有明显的特征差异,其吸收位置和吸收强度基本一致。但在2 000～9 000cm-1红外波段,天然红色绿柱石与水热法合成红色绿柱石的吸收频率差异明显,因此具有独特的鉴别特征。进一步研究表明,天然红色绿柱石在3 500～4 000cm-1之间没有强吸收峰,几乎不含结构水,但在3 300～3 600cm-1之间有非常弱的吸收带(峰值为3 418cm-1),因此有可能有其他形式的水。水热法合成红色绿柱石样品的近红外光谱特征表明,其在3 500～4 000cm-1之间及5 000～5 800cm-1之间均显示有强烈的水的振动吸收:其在5 000～5 800cm-1有弱的Ⅰ型水吸收峰和强Ⅱ型水吸收峰,可以归属为分子水的弯曲和伸缩的合频振动;其在7 000～7 500cm-1之间显示的弱Ⅰ型水的吸收峰和强的Ⅱ型水的吸收峰可以归属为水的倍频振动。因此,水热法合成红色绿柱石中的结构水归属Ⅰ型水与Ⅱ型水的混合型,其在3 500～4 000及5 000～5 800cm-1范围水的近红外吸收光谱特征可作为区别天然和水热法合成红色绿柱石的依据。通过紫外可见光光谱、中红外光谱以及近红外光谱等光谱分析手段可以初步判断红色绿柱石中是否含水、水的赋存状态、以及不同类型水的相对强度和频率,为区分天然与水热法合成红色绿柱石提供诊断性证据。

激光诱导Ti等离子体光谱的时间演化特性研究

利用Nd:YAG激光器产生的1064 nm、10 ns脉冲激光聚焦在空气中的Ti靶,观测了激光诱导Ti等离子体发射光谱.调节激光能量为45 mJ/pulse,分析了时间范围在0到4000 ns的时间分辨发射光谱和谱线轮廓以及展宽.在局部热力学平衡(LTE)条件下,利用Saha-boltzmann图法拟合电子温度,Saha方程计算电子密度,讨论了等离子体电子温度和电子密度随时间的演化规律.结果表明,在所讨论的时间范围内,谱线的强度在延时250 ns处达到最大,250 ns后随着延迟时间的增加减小,电子密度和电子温度在延时1000 ns内快速衰减,1000 ns后衰减速度变慢.

Accurate method based on data filtering for quantitative multi-element analysis of soils using CF-LIBS

To obtain more stable spectral data for accurate quantitative analysis of multi-element,especially for the large-area in-situ elements detection of soils, we propose a method for a multielement quantitative analysis of soils using calibration-free laser-induced breakdown spectroscopy(CF-LIBS) based on data filtering. In this study, we analyze a standard soil sample doped with two heavy metal elements, Cu and Cd, with a specific focus on the line of Cu I324.75 nm for filtering the experimental data of multiple sample sets. Pre-and post-data filtering,the relative standard deviation for Cu decreased from 30% to 10%, The limits of detection(LOD)values for Cu and Cd decreased by 5% and 4%, respectively. Through CF-LIBS, a quantitative analysis was conducted to determine the relative content of elements in soils. Using Cu as a reference, the concentration of Cd was accurately calculated. The results show that post-data filtering, the average relative error of the Cd decreases from 11% to 5%, indicating the effectiveness of data filtering in improving the accuracy of quantitative analysis. Moreover, the content of Si, Fe and other elements can be accurately calculated using this method. To further correct the calculation, the results for Cd was used to provide a more precise calculation. This approach is of great importance for the large-area in-situ heavy metals and trace elements detection in soil, as well as for rapid and accurate quantitative analysis.

Research on batch multielement rapid quantitative analysis based on the standard curve-assisted calibration-free laserinduced breakdown spectroscopy method

This study proposes a batch rapid quantitative analysis method for multiple elements by combining the advantages of standard curve(SC)and calibration-free laser-induced breakdown spectroscopy(CF-LIBS)technology to achieve synchronous,rapid,and accurate measurement of elements in a large number of samples,namely,SC-assisted CF-LIBS.Al alloy standard samples,divided into calibration and test samples,were applied to validate the proposed method.SC was built based on the characteristic line of Pb and Cr in the calibration sample,and the contents of Pb and Cr in the test sample were calculated with relative errors of 6%and 4%,respectively.SC built using Cr with multiple characteristic lines yielded better calculation results.The relative contents of ten elements in the test sample were calculated using CF-LIBS.Subsequently,the SC-assisted CF-LIBS was executed,with the majority of the calculation relative errors falling within the range of 2%-5%.Finally,the Al and Na contents of the Al alloy were predicted.The results demonstrate that it effectively enables the rapid and accurate quantitative analysis of multiple elements after a single-element SC analysis of the tested samples.Furthermore,this quantitative analysis method was successfully applied to soil and Astragalus samples,realizing an accurate calculation of the contents of multiple elements.Thus,it is important to advance the LIBS quantitative analysis and its related applications.

Estimating the grain size of microgranular material using laser-induced breakdown spectroscopy combined with machine learning algorithms

Recent work has validated a new method for estimating the grain size of microgranular materials in the range of tens to hundreds of micrometers using laser-induced breakdown spectroscopy(LIBS).In this situation,a piecewise univariate model must be constructed to estimate grain size due to the complex dependence of the plasma formation environment on grain size.In the present work,we tentatively construct a unified calibration model suitable for LIBS-based estimation of those grain sizes.Specifically,two unified multivariate calibration models are constructed based on back-propagation neural network(BPNN)algorithms using feature selection strategies with and without considering prior information.By detailed analysis of the performances of the two multivariate models,it was found that a unified calibration model can be successfully constructed based on BPNN algorithms for estimating the grain size in the range of tens to hundreds of micrometers.It was also found that the model constructed with a priorguided feature selection strategy had better prediction performance.This study has practical significance in developing the technology for material analysis using LIBS,especially when the LIBS signal exhibits a complex dependence on the material parameter to be estimated.

基于Ar分支比方法的光谱强度响应效率标定研究

利用Nd∶YAG激光器输出的1 064nm激光在大气压环境中产生了Ar等离子体,测量了Ar等离子体的发射光谱,从Ar等离子体发射光谱中筛选出了来自ArⅠ和ArⅡ15个上能级的35条跃迁谱线,基于分支比方法计算了光谱仪的辐射强度响应效率标定系数。此外,利用氘灯和卤钨灯标准光源,对光谱仪辐射强度响应效率进行了标定,得到了针对不同光栅的光谱仪的辐射效率标定系数。用分支比方法获得的辐射强度响应效率标定系数与标准光源得到辐射强度响应效率标定系数具有较好的一致性,其最大相对误差为5.4%。该研究的标定方法可以为一些大型聚变装置的光谱测量的在线标定提供借鉴和参考。

响应面法优化小球藻吸附镉的条件

以吸附率和生物量为指标,在考察单因素实验基础上,利用响应面法确定小球藻吸附Cd^(2+)的最优条件.通过分析得到:各因素对小球藻吸附Cd^(2+)均有显著性影响,影响顺序为c(Cd^(2+))>pH>培养温度.用回归方程预测小球藻吸附Cd^(2+)的最优条件为:温度29.14℃、pH=6.67、c(Cd^(2+)=30.74μmol/L,小球藻的生物量和吸附率分别达到0.71g/L、85.2%.

A Semi-Quantitative Analysis of Essential Micronutrient in Folium Lycii Using Laser-Induced Breakdown Spectroscopy Technique

Abstract In this paper, the capabilities of laser-induced breakdown spectroscopy （LIBS） for rapid analysis to multi-component plant are illustrated using a 1064 nm laser focused onto the surface of folium lycii. Based on homogeneous plasma assumption, nine of essential micronutrients in folium lycii are identified. Using Saha equation and Boltzmann plot method electron density and plasma temperature are obtained, and their relative concentration （Ca, Mg, A1, Si, Ti, Na, K, Li, and Sr） are obtained employing a semi-quantitative method.

A Comparative Study of the Laser Induced Breakdown Spectroscopy in Single- and Collinear Double-Pulse Laser Geometry

Two Q-switched Nd：YAG lasers at 1064 nm wavelength have been employed to produce plasmas on aluminum-based alloy in single- and collinear double-pulse laser induced breakdown spectroscopy （LIBS）. Time resolved technique was used for detecting emission sig- nal by spectrometer equipped with ICCD detector. The intensity calibration of spectral response was performed by using deuterium and tungsten halogen lamps. Time evolution of the plasma temperature and electron number density was investigated in single- and collinear double-pulse experiments. Based on the investigation of plasma parameters, the emission signal enhancement mechanism was discussed qualitatively.

依据不同波段光谱诊断闪电回击通道温度

利用高速无狭缝光栅摄谱仪捕获到的一次闪电光谱资料,结合等离子体光谱理论,选用不同波段的光谱信息估算了闪电回击通道温度.结果表明:用不同波段的谱线组—单电离氮原子(NII)、中性氧原子(OI)和中性氮原子(NI),基于玻尔兹曼图法估算的闪电回击通道平均温度分别为43270 K,17660 K和17730 K;同时用NII和NI两个谱线组,基于萨哈-玻尔兹曼图法估算得到的闪电回击通道平均温度为24770 K.依据闪电通道电晕鞘模型和光谱辐射理论推断,单独选用NII谱线组获得的温度应该是闪电回击通道核心的温度,单独选用NI或OI谱线组获得的温度应该是围绕在闪电回击通道核心周围电晕鞘的温度;同时选用NII和NI谱线组,获得的温度应该是在曝光时间内整个通道截面(包括通道核心和电晕鞘)的平均温度.

Analysis of metallic elements dissolution in the Astragalus at different decocting time by using LIBS technique

Astragalus is an important traditional Chinese herb that has therapeutic potential in the treatment of diseases. In this study, the dissolution of metallic elements during the material decoction process was investigated using laser-induced breakdown spectroscopy(LIBS). The Ca, Mg, Al, and Fe in the drug residues, liquid, and vapor were selected for the study of the transfer of elements after different decocting times. It was found that the intensities of the spectral lines for these elements in the drug liquid increased with increasing decocting times.The contrast trend was observed in the residues and only calcium was detected in the vapor.Furthermore, the relative mass concentrations of Ca, Mg, Al, and Fe in the liquid were quantitatively determined by a combination of the standard addition method and calibrationfree-LIBS method by adding the standard concentration solution of Cu and Cd elements into the drug liquids, it can be found that the maximum error between Cd concentration calculated by internal CF-LIBS and the standard is within 10%. This provides a new method of achieving the on-line monitoring and analysis of metallic elements in the production of traditional Chinese medicines.

Measurement and analysis of species distribution in laser-induced ablation plasma of an aluminum–magnesium alloy

We proposed a theoretical spatio-temporal imaging method,which was based on the thermal model of laser ablation and the two-dimensional axisymmetric multi-species hydrodynamics model.By using the intensity formula,the integral intensity of spectral lines could be calculated and the corresponding images of intensity distribution could be drawn.Through further image processing such as normalization,determination of minimum intensity,combination and color filtering,a relatively clear species distribution image in the plasma could be obtained.Using the above method,we simulated the plasma ablated from Al-Mg alloy by different laser energies under 1 atm argon,and obtained the theoretical spatio-temporal distributions of Mg I,Mg II,Al I,Al II and Ar I species,which are almost consistent with the experimental results by differential imaging.Compared with the experimental decay time constants,the consistency is higher at low laser energy,indicating that our theoretical model is more suitable for the plasma dominated by laser-supported combustion wave.

Analysis of extreme ultraviolet spectral profiles of laser-produced Cr plasmas

Radiation from laser-produced plasmas was examined as a potential wavelength calibration source for spectrographs in the extreme ultraviolet(EUV) region.Specifically, the EUV emission of chromium(Cr) plasmas was acquired via spatiotemporally resolved emission spectroscopy.With the aid of Cowan and flexible atomic code(FAC) structure calculations,and a comparative analysis with the simulated spectra, emission peaks in the 6.5–15.0 nm range were identified as 3 p–4 d, 5 d and 3 p–4 s transition lines from Cr5+–Cr10+ions.A normalized Boltzmann distribution among the excited states and a steady-state collisional-radiative model were assumed for the spectral simulations, and used to estimate the electron temperature and density in the plasma.The results indicate that several relatively isolated emission lines of highly charged ions would be useful for EUV wavelength calibration.