痕量挥发性有机物的高场不对称波形离子迁移谱研究

高场不对称波形离子迁移谱(high-field asymmetric waveform ion mobility spectrometry,FAIMS)技术是一种快速、高灵敏的痕量物质检测技术.利用自制的高场不对称波形离子迁移谱仪分别对丙酮、苯和甲苯样品进行了检测,结果表明三种挥发性物质在谱图中的分离效果优于传统离子迁...     

水体痕量重金属Ni的激光诱导击穿光谱测量研究

以1 064nm波长Nd∶YAG脉冲激光为激发光源,采用高分辨率、宽光谱段的中阶梯光栅光谱仪和ICCD为谱线分离与探测器件,实验研究了水体中痕量镍元素的激光诱导等离子体光谱发射特性和检测限;为了延长水体中金属元素的激光等离子体光谱发射时间、提高光谱检测灵敏度并减小ns激光作用下水滴溅射的影响,实验中以固体圆饼状石墨块为样品基体进行元素富集,通过在基体表面固定区域滴定固定量的已知不同浓度的硝酸镍溶液,烘干并制备待测样品。研究表明,镍的最佳探测延迟时间在700ns左右,元素谱线强度随着样品浓度的增加而增大并在较低浓度下呈现良好的线性关系,计算得到水体中Ni元素的痕量检测限为0.28,研究结果为进一步开展水体痕量重金属的激光诱导击穿光谱测量提供了方法。     

Radiotracer Investigation of the Copper Ore Concentration Process

One of the most difficult operations for control and identification in copper ore concentration process is grain classification in hydrocyclone batteries. In the paper radiotracer investigations of the classification process immediately give values of hydrocyclones parameters with higher accuracy than obtained from conventional methods. Presented paper includes the results of the investigation which was carried out in “Lubin” Copper Mine in Poland.     

Real-space measurement of the potential distribution inside organic semiconductors

We demonstrate that the soft nature of organic semiconductors can be exploited to directly measure the potential distribution inside such an organic layer by scanning-tunneling microscope (STM) based spectroscopy. Keeping the STM feedback system active while reducing the tip-sample bias forces the tip to penetrate the organic layer. From an analysis of the injection and bulk transport processes it follows that the tip height versus bias trace obtained in this way directly reflects the potential distribution in the organic layer.     

Electric dipole moments of water clusters from a beam deflection measurement

The response of (H2O)(n=3-18) clusters to an electric field is studied by beam deflection. All clusters deflect uniformly, behaving as polarizable particles. The effective polarizabilities exceed the electronic component and increase as the clusters are cooled, revealing a large permanent dipole contribution. The results resolve a discrepancy concerning the polarity of water clusters and show that all species access conformations with moments exceeding 1 D. The data show no evidence for a freezing transition down to approximately 120 K, but suggest a shift in the conformer arrangement at n=8-9.     

Radiotracer spectroscopy of deep levels in the semiconductor band gap

Basic electronic properties of semiconductors are determined by defects and impurities. Extremely small relative concentrations may have an effect, if the impurity in question gives rise to a localized electron state having an energy within the band gap of the semiconductor. Among the techniques available to characterize band gap states, the present paper focuses on Deep Level Transient Spectroscopy (DLTS). To derive a definite chemical identification of the band gap states detected, radioactive isotopes are used as a tracer. Characteristic concentration changes of band gap states (detected by repeated DLTS measurements during the elemental transmutation) clearly reveal the involvement of a radioisotope in the formation of a certain defect level. The key issues of a radiotracer experiment are the radioactive doping process and the interpretation of transmutation-induced phenomena. Critical aspects are illustrated on the basis of recent radiotracer-DLTS studies in the semiconductors silicon and silicon carbide. This revised version was published online in August 2006 with corrections to the Cover Date.     

Development of a cw-laser-based cavity-ringdown sensor aboard a spacecraft for trace air constituents

The progress in the development of a sensor for the detection of trace air constituents to monitor spacecraft air quality is reported. A continuous-wave (cw), external-cavity tunable diode laser centered at 1.55 μm is used to pump an optical cavity absorption cell in cw-cavity ringdown spectroscopy (cw-CRDS). Preliminary results are presented that demonstrate the sensitivity, selectivity and reproducibility of this method. Detection limits of 2.0 ppm for CO, 2.5 ppm for CO₂, 1.8 ppm for H₂O, 19.4 ppb for NH₃, 7.9 ppb for HCN and 4.0 ppb for C₂H₂ are calculated. Received: 3 April 2002 / Revised version: 3 June 2002 / Published online: 21 August 2002 RID="*" ID="*"Corresponding author. Fax: +1-202/994-5873, E-mail: Houston@gwu.edu     

梯度折射率球透镜的制备及其光线轨迹测试

自麦克斯韦鱼眼透镜理论模型提出后,长期以来学术界一直以为它只是一种绝对光学仪器,在实践中并没有应用的可能。但通过对麦克斯韦鱼眼微球透镜的理论研究表明,在一定条件下,它具有良好的成像性能和耦合效率。根据菲克定律推导出梯度折射率球透镜的折射率分布函数。并且熔制了含Li+硅酸盐玻璃和采用槽沉法以及Na+/Li+离子交换法制备直径为0.3—3.0mm的梯度折射率球透镜。通过干涉法测得了梯度折射率球透镜的折射率分布曲线,并研究了光线通过梯度折射率球透镜的轨迹。研究结果表明:在590℃,离子扩散系数为3.07×10-6mm2/s;所制备的梯度折射率球透镜的折射率分布是抛物线分布,并且和理论分析相吻合;梯度折射率球透镜的光线轨迹满足椭圆方程。     

Analysis of trace elements in water by ESCA

A new method for the analysis of trace elements in water using ESCA (X-ray photoelectron spectroscopy) is described. The method is applicable to the si     

Accuracy and analysis of long-radius measurement with long trace profiler

The long trace profiler(LTP) is proposed to measure radius of curvature(R) and surface figure of a longradius spherical surface in an optical shop.Equipped with a motorized rotary stage and a two-dimensional tilt stage,the LTP scans the full aperture and calculates the absolute radius of curvature of each scanning line based on the least square method.Nonlinear error and manufacture error difference between center and the edge are obtained by comparing R results.The R-limit is validated and expressed as D/R,where D is the aperture of the mirror under test.A full-aperture three-dimensional figure is also reconstructed based on triangle interpolation.     

Intraneuronal investigations of organic components and trace elements with the use of synchrotron radiation

Three techniques based on synchrotron radiation microbeam analysis were applied to biochemical investigations of human central nervous system (CNS) tissue. Thin tissue slices representing Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and control cases were studied. Synchrotron radiation microbeam x‐ray fluorescence (micro‐SRXRF) was applied to the analysis of the elemental distribution inside single nerve cells. Investigation of copper oxidation state was performed with the use of micro x‐ray absorption near‐edge structure spectroscopy (micro‐XANES). Moreover, the organic components of the tissues were analyzed by means of synchrotron radiation Fourier transform infrared microspectroscopy (SR‐FTIRM). Topographic differences in elemental composition were observed for the nerve cell body. Higher levels of Fe, Zn and Ca were found for the neurons of PD cases in comparison with the control group. The IR spectra measured in neurons of PD, ALS and control cases showed differences in absorption bands associated with characteristic groups of selected biological molecules. Additionally, results of SR‐FTIRM measurements indicated inhomogeneous accumulation of the main organic components in PD nerve cells, in contrast to the control cases. Copyright © 2005 John Wiley & Sons, Ltd.     

Direct measurement of the triplet exciton diffusion length in organic semiconductors

We present a new method to measure the triplet exciton diffusion length in organic semiconductors. N,N'-di-[(1-naphthyl)-N,N'-diphenyl]-1,1'-biphenyl)-4,4'-diamine (NPD) has been used as a model system. Triplet excitons are injected into a thin film of NPD by a phosphorescent thin film, which is optically excited and forms a sharp interface with the NPD layer. The penetration profile of the triplet excitons density is recorded by measuring the emission intensity of another phosphorescent material (detector), which is doped into the NPD film at variable distances from the injecting interface. From the obtained triplet penetration profile we extracted a triplet exciton diffusion length of 87±2.7 nm. For excitation power densities >1 mW/mm(2) triplet-triplet annihilation processes can significantly limit the triplet penetration depth into organic semiconductor. The proposed sample structure can be further used to study excitonic spin degree of freedom.     

Investigation on infrared laser absorption spectroscopy measurement of acetylene trace quantities

A laser-based infrared spectrometer was developed for use in high-resolution spectroscopic analysis of trace gases in the atmosphere. Continuous wave, broadly tunable coherent infrared radiation was generated from 8 to 19 μm in a gallium selenide crystal by laser difference-frequency mixing. Measurements of acetylene trace concentrations using laser absorption spectroscopy are reported. The measurements have been performed by using the P(21), Q(11), and R(9) lines of the ν₅ band, respectively, in order to investigate optimal detection conditions: a trade-off choice between higher line absorption strength for sensitive detection and better spectral discrimination from lines overlapping for open path trace-gas monitoring applications. Minimum detectable concentrations are compared under different experimental conditions. The ν₅ R(9) line seems to be close to optimum in terms of absorption strength and freedom from spectral interference for spectroscopic detection of acetylene trace concentration at atmospheric pressure.     

自发喇曼成像法在线测量流场组分浓度

介绍了自发喇曼成像技术实时监测流场组分浓度的方法,利用Nd：YAG脉冲激光器以及ICCD和光谱仪对大气进行了不同实验条件的测试,得到了影响谱线强度及测试精度的几个因素;得到了大气流场各主要成分的自发喇曼散射光谱和绝对浓度,测量误差小于8%。该技术可望在氧碘化学激光器单重态氧发生器物种浓度测定时得以应用以改善O2(1Δ)浓度测试精度较低的现状。     

Contributions to the Optimization of a Caprolactam Production Plant by Radiotracer Techniques

Residence time spectra and material distributions in an operating caprolactam production plant were measured by means of sodium 24, bromine 82 and technetium 99m. The results of the tracerexperiments contributed to an optimization of the plant.     

自发喇曼成像法在线测量流场组分浓度

 介绍了自发喇曼成像技术实时监测流场组分浓度的方法,利用Nd：YAG脉冲激光器以及ICCD和光谱仪对大气进行了不同实验条件的测试,得到了影响谱线强度及测试精度的几个因素;得到了大气流场各主要成分的自发喇曼散射光谱和绝对浓度,测量误差小于8%。该技术可望在氧碘化学激光器单重态氧发生器物种浓度测定时得以应用以改善O₂(¹Δ)浓度测试精度较低的现状。     

太湖典型湖区水体溶解有机质的光谱学特征

应用荧光光谱、紫外光谱及多种紫外参数等光谱学手段对太湖水体溶解有机质(DOM)进行分析测定,探讨太湖典型湖区水体中DOM的来源及其影响因素。结果表明:不同湖区水体DOM组成特性呈现出一定的区域特征,位于入湖河流的T1点和T2点所代表的竺山湾湖区,结构复杂的大分子物质和腐殖质类物质含量较多,这些区域受多重来源包括生物来源、陆源及生产生活污水的影响较大;以T3为代表的梅梁湾湖区、T4为代表的贡湖湾湖区和T5所处的湖心区其DOM复杂化程度相对较低;而T6点代表的东太湖湖区,因受外界环境的影响较小,以结构简单的类蛋白物质含量居多。     

Effect of buffer gases on the performance of SO2 trace measurement based on photoacoustic spectroscopy

In this experimental work a laser photoacoustic spectrometer designed and fabricated. System sensitivity for detection of SO₂ and NO₂ was measured. Resonance frequency variation versus pressure increase of Nitrogen, Argon, Helium and Air buffer gases was studied. Results show that, sensitivity of system for SO₂ and NO₂ are 353 ppb and 963 ppb respectively. It was shown that resonance frequency for Nitrogen, Argon, and Air buffer gases was not noticeably varied by buffer gas pressure increasing, but for Helium, resonance frequency not only is not in range of three other gases, but also grows by pressure increasing. The system noises were damped preparing two buffer chambers.