Half-Width Integral Method for Gas Concentration Measuring in Tunable Diode Laser Absorption Spectroscopy

ABSTRACT

We analyze the influence of random errors and absorption shape fitting errors on gas concentration measurement in tunable diode laser absorption spectroscopy. We then propose a new data processing method according to the characteristic of random errors and fitting absorption shape. This method only uses the integral value within the half width at half maximum of the fitting absorption shape to determine the gas concentration in actual measurements. Meanwhile, the O₂ transition at 13,150.197 cm^?1 is selected to measure the O₂ concentration using this method. Compared with the traditional method, the method established in this paper can accurately measure O₂ concentration.     

Study of Spectroscopic Properties of Yb-doped Calcium Fluorapatite

The spectroscopic performance of Yb-doped calcium fluorapatite (Yb:FAP) was assessed by measuring polarization absorption spectra, polarization emission spectra and fluorescence lifetime. The emission cross section has been evaluated using the absorption cross section and principle of reciprocity. The π polarization absorption and emission cross sections of Yb3+ in FAP are found to be substantially larger than those of other Yb-doped media. Favorable spectroscopic parameters show that Yb:FAP crystal is more desirable for many diode-pumped solid state laser application with low- and medium-power in the near future.     

Study of Spectroscopic Properties of Yb-doped Calcium Fluorapatite

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Calculation of the Probabilities of Nonradiative Transitions from Deep Impurity Centers with Account for Electron–Phonon Interaction

Using the form–function of optical transition as a basis, we suggest an algorithm for calculating the field dependences of the probability of nonradiative transitions. The algorithm worked out is compared with an experiment carried out for the V _Ga S _As complex in gallium arsenide. The conclusion is drawn that the proposed scheme of calculating the field dependences is preferable to the methods based on a single–coordinate model.     

高分辨分子吸收光谱中的波长校准方法

本文提出高分辨分子吸收光谱中，以碘分子谱作为参考标准的波长校准方法，编制了以人机交互方式自动完成波长校准的软件，并应用于16 422-17 896cm^-1可见光波段范围内的N2^ 分子离子的高分辨吸收谱线的波长校准，结果表明其绝对准确度可达0.006cm^-1。     

差分吸收光谱技术测量氯气的数据处理方法研究

基于差分吸收光谱(DOAS)技术,结合自主搭建的一套小型便携式DOAS实验系统,开展了对氯气的实验测量。在处理氯气的标准截面时,比较了两种不同的高通数字滤波方法：三角函数滤波和多项式拟合滤波。实验证明采用后一处理方法能够更加准确反演出氯气的浓度。模拟计算的结果显示,采用五阶多项式处理的结果的误差较小;在不同样品池内的测量结果显示,利用该方法测量氯气的线性度达到0.996 1;实际的一条谱的反演结果显示拟合谱与测量谱基本重合,且剩余噪声谱的峰峰值最大值<5‰;给出整个实验过程中可能的误差主要来源。综合以上的实验结果表明,利用DOAS技术采用多项式拟合处理的方法可以实现对于氯气的检测。     

The Collocation Method and the Splitting Extrapolation for the First Kind of Boundary Integral Equations on Polygonal Regions

In this paper, the collocation methods are used to solve the boundary integral equations of the first kind on the polygon. By means of Sidi's periodic transformation and domain decomposition, the errors are proved to possess the multi-parameter asymptotic expansion at the interior point with the powers $h_{i}^{3}(i=1,...,d)$, which means that the approximations of higher accuracy and a posteriori estimation of the errors can be obtained by splitting extrapolations. Numerical experiments are carried out to show that the methods are very efficient.     

Optical Absorption Study on the Conversion and Restoration of Color Centers in Pure KCI Crystals

The conversion and restoration processes of colour centers in pure KCI crystals were studied by optical absorption measurements. When the sample is heated the aggregative centers in it begin to dissolve to F centers, and the opposite process will take place, i.e. F centers will aggregate to form F₂, F₃, F₄centers if the samples are cooled down. It was found that the conversion and restoration processes are dependent on the annealing temperature and time. In our experiment, the samples were treated at various temperatures and time. In addition the restoration process for the 350°C treated sample was studied live. We found that the higher the annealing temperature is the slower the restoration in the samples proceed, and the conversion process maintained for a few minutes even after annealing treatment.     

无网格方法中的背景积分方案及单颗粒下降过程的数值模拟

在用无网格方法对有边界移动的气固两相流动进行数值模拟时发现,如果采用背景积分网格对求解域进行积分,将会产生压力场的数值振荡,使计算结果失真.详细分析了产生这种数值振荡的原因,提出了解决方案,并计算了一个颗粒在管道内的下降过程.计算结果表明,提出的解决方案能有效地降低压力场的数值振荡,从而使无网格方法能应用于气固两相流动的直接数值模拟.     

Spectral-Luminescent Properties of Cationic Indotricarbocyanine Dyes in Cancerous Cells and Solutions

The spectral-luminescent properties of symmetrical indotricarbocyanine dyes with the same cation and different anions (Br^–, BF₄ ^–) in cancerous HeLa cells, an isotonic solution of NaCl, and organic solvents have been investigated. It is shown that when these dyes are present in cells in nontoxic concentrations, they are in a monomeric state, they are localized in the region with a low dielectric permeability, bonded to biological macromolecules, and do not make contact with an aqueous medium. It has been established for the first time that the molecules of the polymeric dyes are present in cells predominantly in the form of contact ion pairs, and in a dye with the Br^– anion the presence of free cations or solvately separated ionic pairs is revealed. It is shown that the shift of the ion equilibrium toward contact ion pairs for the dyes in the cells (as compared to the low-polarity organic solvents) can be due to the fairly high concentration of salts in the biosystem.     

Experimental determination of effective stimulated emission cross-section in a diode pumped Nd:YVO4 micro-laser at 1064 nm with various doping concentrations

A practical method is described and used for determination of the effective stimulated emission cross-section (σ_e) in an operating diode pumped Nd:YVO₄ micro-laser at 1064 nm with various doping concentrations. In this method a micro-laser is formed by keeping a small piece of the sample in a plane–plane resonator under semi-monolithic configuration and a fiber coupled diode laser (808 nm) was used for pumping. The pump power induced thermal lensing effect was used to make the cavity stable. In thermally stabilized solid-state lasers the cavity parameters change dynamically with the pump power and hence the overlap integrals become a function of the absorbed pump power. In our method the overlap integrals were estimated by measuring the thermal lens focal length at the threshold. The value of σ_e of Nd:YVO₄ crystal with different doping concentrations obtained by this method were in well agreement with the reported values.     

激光诱导击穿光谱结合标准加入法定量分析未知样品中铅含量

利用激光诱导击穿光谱结合标准加入法定量分析了铅蓄电池厂含铅污泥中重金属铅元素含量, 标准加入法有效避免了外标法与内标法制作标准曲线时基质不同对LIBS检测结果的影响, 且样品处理过程简单。实验采用中心波长为1 064 nm的Nd∶YAG脉冲激光器作为激发光源, 以高分辨率、宽光谱段的中阶梯光栅光谱仪和增强型电荷耦合器件为谱线分离与探测器件, 选取铅的PbⅠ: 405.78 nm特征谱线作为分析线, 以FeⅠ: 404.58 nm特征谱线作为内标线进行结果计算。预实验确定较佳的实验条件后(激光脉冲能量: 128.5 mJ, 延时: 2.5 μs, 门宽: 3 μs), 对铅蓄电池厂的未知铅泥样品中铅元素进行定量分析, 结果表明加入铅在0~25 000 mg·kg-1范围内谱线不会产生自吸收, PbⅠ: 405.78 nm信号强度与铅加入量呈很好的线性关系, 由此确定合适的铅加入量为0~25 000 mg·kg-1。在此基础上配制四个样品, 基质均为铅蓄电池厂含铅污泥, 加入铅浓度分别为5 000, 10 000, 15 000, 20 000 mg·kg-1, 每个样品设置三个平行样, 验证实验重复性及可靠性, 并与ICP-MS检测结果对比, 结果直线外推误差为-14.8%。12个样品单次计算结果误差介于为-24.6%~17.6%之间, 含铅量平均值为43 069 mg·kg-1, 相对误差为-2.44%。     

THz radiation generation via the interaction of two‐colour ultra‐short laser pulses with SO2 and NH3 gases

In this work, using a two‐dimensional particle‐in‐cell Monte Carlo collision computation method, terahertz (THz) radiation generation via the interaction of two‐colour, ultra‐short, high‐power laser pulses with the polyatomic molecular gases sulphur dioxide (SO₂) and ammonia (NH₃) is examined. The influence of SO₂ and NH₃ pressures and two‐colour laser pulse parameters, i.e., pulse shape, pulse duration, and beam waist, on the THz radiation generation is studied. It is shown that the THz signal generation from SO₂ and NH₃ increases with the background gas pressure. It is seen that the THz emission intensity for both gases at higher laser pulse durations is higher. Moreover, for these polyatomic gases, the plasma current density increases with increase in the laser pulse beam waist. A more powerful THz radiation intensity with a larger time to peak of the plasma current density is observed for SO₂ compared to NH₃. In addition, many THz signals with small intensities are observed for both polyatomic gases. It is seen that for both SO₂ and NH₃ the generated THz spectral intensity is higher at higher gas pressures.     

基于旋转液体特性实验的激光双次反射法测重力加速度

旋转液体特性实验是大学物理实验中典型的综合实验项目,本文利用激光束在旋转液体表面的双次反射时的特性,确定了测量重力加速度的新方法。通过对比实验发现,本设计减少了原有单次激光反射测量重力加速度时的物理量数目,并有效提高了测量结果的精确度。     

Numerical Study of Open Slot Lines with Asymmetrically Placed Strip Conductor in 37.5–78 GHz Frequency Band

Slot lines with strip conductors asymmetrically placed on a finite size substrate have been rigorously studied by means of the singular integral equation method (SIE). Dependences of the propagation constant on the frequency for different slot line sizes (substrate width, strip conductor width as well as the distance from the substrate edge, slot width and substrate thickness) were determined in the 37.5 – 78 GHz frequency. What we analized was a) how the substrate thickness and slot width affected the number of modes propagating in the slot line and b) what the size of the line should be to ensure propagating of only one mode (this is important in practice).