Statistical properties of laser-induced fluorescence signals

We point out the influence of the different noise sources which occur in the detection of the fluorescence signal induced by a laser in an atomic beam. We have developed a theoretical model which takes account of the atomic shot noise, photon noise, laser-frequency noise and a partition noise linked to the imperfect detection of the fluorescence photons. The calculations have been performed for two- and three-level atomic systems. We detail the own contribution of each noise source and give some predictions concerning the value of the fluorescence signal to noise ratio. We determine predominance domains of each noise source which depend on the values of key parameters such as the atomic flux intensity and the laser spectral linewidth. We particularly show that the laser-frequency noise, which induces a coupling between the emission of fluorescence photons by various atoms, leads to a saturation of the S/N ratio for intense atomic fluxes. Moreover, we point out that the optical pumping process associated with a three level atomic system leads to an interesting laser-noise filtering effect.     

Theoretically study on measurement of velocity distribution by means of laser induced fluorescence

Based on two-level atomic density matrix movement equation and emitting operator, the physical model is established for laser induced moving atomic resonant fluores cence. Theoretically study showsthat the measurement of atomic velocity distribution by means of laser induced fluorescence is only valid when the physical factors, such as atomic natural line width, laser power, laser line width, is suitably selected.     

Determination of spatial temperature distributions in a laminar premixed ethylene/air flame by laser-induced atomic fluorescence

A quick and simple detection system for spatially resolved temperature measurements in flames based on laser-induced thermally assisted atomic line fluorescence of seeded rubidium atoms is described. The fluorescence light from two atomic states is dispersed and simultaneously recorded by a CCD camera. The fluorescence ratio distributions lead directly to absolute temperature distributions. The practical use, the spatial and temperature resolution and error limits of the method are discussed and compared with other procedures for temperature measurements.     

Imaging an atomic beam using fluorescence

A fluorescence detection scheme is applied to image an atomic beam. Using two laser diodes as the sources of detection light and pumping light respectively, the fluorescence image of the atomic beam is then observed by a commercial CCD-camera, which is corresponding to the atomic state and velocity distribution. The detection scheme has a great utilization in the experiments of cold atoms and atomic optics.     

空心阴极灯激发的微波等离子体炬原子/离子荧光光谱研究--钙的原子/离子荧光光谱

用强短脉冲供电技术的空心阴极灯作激发源、微波等离子体炬作原子／离子化器，建立了原子／离子荧光光谱实验装置。详细研究了微波等离子体功率、观察高度、空心阴极灯电流等因素对原子／离子荧光信号强度的影响，测量了系统对Ca的原子／离子荧光光谱的检出限。     

Comparison of Detection Limits in Atomic Fluorescence and Absorption Spectroscopy

Dagnall, Taylor, and West have recently compared detection limits for a number of metals in atomic fluorescence and absorption spectroscopy and have concluded that “atomic fluorescence measurements using an electrodeless discharge tube are inherently more sensitive than those obtainable by atomic absorption measurements”. Likewise West and Williams have compared the two techniques for magnesium²and silver³, using high-intensity hollow-cathode lamps as sources, and have found much lower detection limits in fluorescence than in absorption.     

蒸气发生-原子荧光光谱法测定中草药中不同形态的汞

建立了蒸气发生-原子荧光光谱法测定中草药复方方剂原生药、残渣、悬浮态、可溶态的无机汞和有机汞的方法。研究了仪器的工作条件、试剂浓度、增感剂对汞原子荧光强度的影响及有机汞的氧化条件,探讨了共存离子对汞测定的干扰和消除方法,利用本方法成功地对万氏牛黄清心方剂中的汞进行了形态分析。方法检出限为7.6 ng·L-1,RSD为1.56%～3.28%,回收率为90.3%～110.3%。     

Excitation transfer from second to first resonance line of potassium observed in hot atomic vapor

We present experimental investigation on the fluorescence profiles observed by excitation of the hyperfine transitions of the second resonance line of potassium with a wavelength of 404.4 nm in dependence on the atomic density. This leads to both direct decay of the excited level population to the ground state (violet fluorescence), and to cascade decay via the first resonance lines (infrared fluorescence). It has been shown that the behavior of these two fluorescence profiles is different: increasing the atomic density, the violet fluorescence profile exhibits a well-pronounced self-absorption dip, while the infrared line does not show any narrow-width reduced absorption structure. Moreover, the profiles of the infrared line have a higher signal-to-noise ratio than that of the violet line. Our investigations show that beside atomic population, atomic polarization is also transferred by the cascade transitions. This is evidenced by registration of coherent magneto-optical resonances at the two fluorescence lines. The signal-to-noise ratio of these resonances registered at the first resonance line is significantly higher than at those obtained at the second resonance line. The proposed study makes it possible to examine cascade transitions in alkali atoms, particularly the preservation of atomic polarization, i.e. the coherence transfer by cascade transitions.     

偏振光激发的Sr原子电偶极辐射

原子与激光场相互作用产生的自发辐射可以用经典电偶极辐射理论很好的描述.通过改变与Sr原子束相互作用激光的偏振方向,分析探测Sr原子束荧光强度的变化,测定了在远场区的电偶极辐射特性.Sr原子电偶极子在远场区辐射能量的空间方向分布满足sin2θ关系,利用这一规律可以有效地探测到最强的荧光光谱.     

An Experimental Study of the Fluorescence Spectrum of Cesium Atoms in the Presence of a Buffer Gas

A direct experiment is performed to determine the quantum efficiency of a cesium fluorescence filter. The fluorescence spectra of cesium atoms are recorded under excitation of the upper states of the second resonance doublet with a Bell–Bloom cesium lamp. Introduction of different noble gases into the cell with cesium leads to the appearance of additional fluorescence photons. It is found that a fluorescence filter based on atomic cesium vapor with addition of helium in the working cell has the highest efficiency and response rate of all known fluorescence filters based on alkali-metal atomic vapors.     

X射线荧光光谱中散射效应对荧光强度的贡献研究

采用理论计算和实验测定的方法研究了在纯元素样品、BaB二元样品及熔融片样品中三种散射效应对荧光强度的贡献(包括相干散射X射线激发的荧光强度、非相干散射X射线激发的荧光强度以及其他方向的一次荧光X射线被散射进探测方向的强度)大小及其变化规律。研究结果表明,三种散射效应对荧光强度的贡献大小与所研究元素原子特征谱线的能量及样品的基体有关,元素原子的特征谱线能量越高,散射效应对荧光强度的贡献越大;轻基体样品中散射效应对荧光的贡献比重基体样品大。实验证明,将散射效应包括在基本参数法的理论计算中可以有效地提高理论计算的准确度。     

Experimental evidence of excited multicharged atomic fragments coming from laser-induced coulomb explosion of molecules

Direct experimental evidence is presented for the production of excited multicharged atomic fragments in the laser-induced Coulomb explosion of molecules. The comparison of the fluorescence signals of several atomic and molecular species shows that the excited fragments come from transient excited multicharged molecules. The atomic fluorescence spectra recorded with NH3, N2, and N2O, in the 50-120 nm wavelength range, show that the excitation increases noticeably from NH3 to N2O. This effect is interpreted in terms of the initial electronic configuration, which favors a stronger excitation when the electronic density is more delocalized on the molecular nuclear structure.     

Die kinetischen Eigenschaften der Elektronen des anisothermen homogenen stationären Neon-Plasmas im Ionisierungsgradbereich von 10−9 bis 10−2

The time dependence of the spectral and spatial energy density of the fluorescence radiation of an atomic system generated by the resonance scattering of an intense laser pulse was calculated. Particularly the influence of the duration and the intensity of the incident laser pulse and of the atomic relaxation constants upon the fluorescence radiation has been studied.     

中国原子光谱发展近况概述

原子光谱技术作为现代分析检测技术中的一个重要组成部分,在分析领域中占据着举足轻重的地位,而其发展也反映了分析技术的不断改革与创新。综述了中国原子光谱技术近15年来(2000年—2014年)的研究与应用进展。内容涉及原子光谱的多个分支领域,包括原子发射光谱(atomic emission spectrometry,AES),原子吸收光谱(atomic absorption spectrometry,AAS),原子荧光光谱(atomic fluorescence spectrometry,AFS),X射线荧光光谱(X-ray fluorescence spectrometry, XRF)以及原子质谱(atomic mass spectrometry,AMS)五种原子光谱技术,重点关注各技术在检测方法上的创新及其在环境样品、生物样品、食品饮料以及地质材料等相关领域中的应用,并对原子光谱分析中利用到的各种联用技术进行了简要介绍。最后展望了今后我国原子光谱技术的发展方向。     

冷原子荧光光谱法测定3种中药材中的痕量汞

采用硝酸-双氧水体系及高压消解法处理样品,建立了氢化物发生-冷原子荧光光谱法测定中药材中的痕量汞的测定方法,研究了仪器工作条件、介质酸及浓度、还原剂硼氢化钾浓度对测量结果的影响并进行了优化,在最佳实验条件下对3种云南产地中药材进行了测试,汞的校准曲线在0—10μg.L-1范围内线性良好,相关系数为0.9999,方法的检出限为2.9ng.L-1,RSD为1.8%,测定的3种中药材中的汞含量为5.62—17.29ng.-g 1,加标回收率为90.3%—105.2%。     

Study on Atomic Fluorescence Spectrometry Excited by Synchrotron Radiation

将同步辐射作为原子荧光的新型激发光源,建立了同步辐射原子荧光光谱分析装置,并对具体实验条件,如气体流速、分析物酸度、预还原试剂以及氢化物发生体系浓度等进行优化. 利用该装置测定了原子荧光代表分析物?砷的同步辐射原子荧光激发谱线. 在主要的10条谱线中,7条与现有文献记载十分吻合,其中4条系首次以原子荧光手段获得,另3条系首次发现. 对谱线所对应的激发电位以及可能的跃迁过程进行了分析,特别是对234.99 nm强峰的产生机理进行了探讨,并建立了能级跃迁模型.     

Application of Atomic Fluorescence Spectrometry to the Determination of Sulfide Ion in Sewage Waters

Atomic fluorescence spectrometry and direct flame photometry are evaluated as alternative methods for the determination of inorganic sulfide in municipal sewage. The sulfide is volatilized as H₂S from the sewage influent or effluent sample, which has been stabilized by a 0.05 M sodium ascorbate buffer. Both flame spectrometric methods are more sensitive than the standard colorimetric method, but quantification is easier for the atomic fluorescence method. The latter technique has a wide linear dynamic range and is unaffected by a gradual increase in the residual H₂S level in the system. The atomic fluorescence signal is also unaffected by the presence of volatile hydrocarbons in the sewage. The results obtained with the fluorescence method agree well with those obtained with the standard method, while the flame photometric results are low. Studies on the effect of metal ions on the fluorescence signal indicate that the method determines “total sulfide”.     

原子光谱分析的进展及其应用

文章综述了原子光谱领域分析仪器及分析方法的最新研究进展;例如原子吸收光谱(AAS)、原子发射光谱(AES)、原子荧光光谱(AFS)、激光诱导击穿光谱(LIBS)以及原子质谱(AMS)等,重点关注在食品、医药及其相关领域中的应用。近年出现的芯片实验室和微等离子体,促进了原子分析仪器的微型化发展,而激光及其联用技术在形态分析中的应用仍颇为流行。     

Characterization of Conifers and Their Products by Optical Atomic Spectrometry

Abstract

Conifers are primarily evergreen trees that are widely distributed; admired for their beauty; used as biomonitors for elements; processed for lumber, paper, fuel, and other products; and employed for food and medicinal products. Optical atomic spectrometry includes the widely used elemental analysis techniques of atomic absorption, atomic emission, and atomic fluorescence. This review considers applications of optical atomic spectrometry for conifers and their products. The goal is to assemble these diverse applications to assist analytical chemists and associated scientists in the development of methodology. The conclusion summarizes these studies and forecasts future developments.     

Determination of the atomic density of rubidium-87

Atomic density is a basic and important parameter in quantum optics, nonlinear optics, and precision measurement.In the past few decades, several methods have been used to measure atomic density, such as thermionic effect, optical absorption, and resonance fluorescence. The main error of these experiments stemmed from depopulation of the energy level, self-absorption, and the broad bandwidth of the laser. Here we demonstrate the atomic density of87 Rb vapor in paraffin coated cell between 297 K and 334 K mainly using fluorescence measurement. Optical pumping, anti-relaxation coating, and absorption compensation approaches are used to decrease measurement error. These measurement methods are suitable for vapor temperature at dozens of degrees. The fitting function for the experimental data of87 Rb atomic density is given.