Monochromatization of resonance radiation in Zeeman atomic absorption spectrometry

Two methods of background correction in atomic absorption spectrometry with nonselective atomic effects are investigated: first, with a source possessing a continuous spectrum and, second, that of correction based on the Zeeman effect. The parameters of the monochromator, which was developed expressly for Zeeman atomic absorption spectrometry, are considered. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 20–24, September, 2007.     

Development and application of acousto-optic background correction for inductively coupled plasma atomic emission spectrometry

In two configurations, a solid-state acousto-optic (AO) deflector or modulator is mounted in a 0.5 m monochromator for background correction with inductively coupled plasma atomic emission spectrometry (ICP-AES). A fused silica acousto-optic modulator (AOM) is used in the ultraviolet (UV) spectral region applications while a glass AO deflector (AOD) is used for the visible (VIS) region. The system provides rapid sequential observation of adjacent on- and off-line wavelengths for background correction. Seventeen elements are examined using pneumatic nebulization (PN) and electrothermal vaporization (ETV) sample introduction. Calibration plots were obtained with each sample introduction technique. Potable water and vitamin tablets were analyzed. Flame atomic absorption (FAA) was used to verify the accuracy of the AO background correction system.     

Electrical and optical properties of copper-complexes thin films grown by the vacuum thermal evaporation technique

In this work, the synthesis and characterization of molecular materials formed from K₂[Cu(C₂O₄)₂], 1,8-dihydroxyanthraquinone and its potassium salt are reported. These complexes have been used to prepare thin films by vacuum thermal evaporation. The synthesized materials were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), fast atomic bombardment (FAB+) mass and ultraviolet–visible (UV–vis) spectroscopy. Electrical transport properties were studied by dc conductivity measurements. The electrical activation energies of the complexes, which were in the range of 0.36–0.65 eV, were calculated from their Arrhenius plots. Optical absorption studies in the 100–1100 nm wavelength range at room temperature showed thin films' optical band gaps in the 2.3–3.9 eV range for direct transitions. On the other hand, strong visible photoluminescence (PL) at room temperature was noticed from the thermally-evaporated thin solid films. The PL of all investigated samples were observed with the naked eye in a bright background. The PL and absorption spectra of the investigated compounds are strongly influenced by the molecular structure and nature of the organic ligand.     

AAS、ICP-AES和HG-AFS在水质检测中的比较

对水质检测中测定金属元素经常使用的三种分析方法:原子吸收法(火焰法和石墨炉法)、电感耦合等离子体发射光谱法和氢化物发生-原子荧光光谱法。光谱的主要优缺点进行了比较。重点比较的内容有:水样的预处理步骤、干扰因素(包括光谱干扰、化学干扰、电离干扰)、各元素的检出限、线性范围、精密度和同时测定多元素能力的比较。     

Automatic correction of continuum background in laser-induced breakdown and Raman spectrometry

The goal of this work was the development and evaluation of an algorithm for the approximation and automatic subtraction of continuum backgrounds in laser-induced breakdown and Raman spectra. The background correction algorithm was applied to simple and complex spectra and its effect on identification accuracy was studied. Linear correlation was used for the identification of plastic samples using both laser-induced breakdown and Raman spectra. For both techniques, the algorithm successfully eliminated continuum background without compromising spectral integrity. A significant improvement in the percentage of correct plastic identifications was observed for Raman spectra. The approach should be applicable to a wide range of background correction problems in atomic and molecular spectroscopy.     

Study of protein adsorption on octacalcium phosphate surfaces by molecular dynamics simulations

This study numerically studies absorption of human serum albumin (HSA) and basic protein lysozyme (LSZ) on crystallographic planes of octacalcium phosphate (OCP), an essential bioactive calcium phosphate. The molecular simulations include constructing atomic structure of OCP crystallographic planes and representative segments of HSA and LSZ with three different initiate orientations respect to OCP planes. The simulation reveals the dynamic process of the protein absorption. The absorption behavior of proteins is quantified by the interaction energy between proteins and OCP planes and the strain energy of proteins in absorption. The results show that absorption interaction energy of basic LSZ is higher than that of acidic HSA, which indicates that LSZ is more favorable to adsorb onto OCP surface than HSA. The interaction energies change with the OCP crystallographic planes, the trend of changes for both proteins are similar, that is OCP (001) > OCP (111) > OCP (110) > OCP (100), which is corrected with surface energy variation of crystallographic planes. The strain energy strongly depends on the orientations of the proteins before absorption, but weakly depends on crystallographic planes. The simulation results provide useful significant information for predicting/designing interface between bioceramic materials and organic tissues as well as for understanding the mechanism of the osteoinductivity at an atomic level.     

Co-existing of dressed non-linear gain and electromagnetically induced absorption

The dressed parametric four-wave mixing (FWM) process has been investigated in hot atomic rubidium vapor. We use a strong pumping field to generate entangled photon pairs of spontaneous parametric FWM (SP-FWM) which can be enhanced by an external dressing effect. Seeding probe beam into the Stokes or anti-Stokes (SP-FWM) channel will form the parametric amplified FWM (PA-FWM) process, then the non-linear gain and electromagnetically induced absorption (EIA) are observed, caused by the internal dressing effect. However, with scanning of pumping field the absorbing background will vanish, which will result in drastic increase in PA-FWM signal gain.     

Synthesis and investigation of π-conjugated azomethine self-assembled multilayers by layer-by-layer growth

Layer-by-layer formation for π-conjugated azomethine multilayers bonded on substrates was investigated. The multilayers were synthesized using ethanol (EtOH) and dichloromethane (DCM) as reaction solvents. The multilayer characteristics were analyzed using UV-vis absorption spectroscopy, ellipsometric thickness, and atomic force microscopy. The absorption spectra and ellipsometric thicknesses of multilayers formed using EtOH and DCM were compared. The results indicate that EtOH is more suitable than DCM for such layer-by-layer formation. In addition, bandgaps estimated from the absorption edge of multilayers were investigated. The results indicate that the bandgap decreases as the number of benzene rings contained in the molecular chain of the multilayer increases. Also, a multilayer with four benzene rings bonded on a substrate had a bandgap close to that of a polymer with a similar chemical structure.     

Two-dimensional temperature measurements in flames using filtered Rayleigh scattering at 254 nm

Two-dimensional temperature measurements using filtered Rayleigh scattering (FRS) have been demonstrated. A tunable single-longitudinal-mode alexandrite laser was employed to provide the tunable narrow-line-width ultraviolet laser beam at 254 nm. Isotopic-enhanced mercury was utilized as an ultraviolet atomic filter. The strong absorption of the filter enabled effective suppression of elastic background. The transmission curve of the mercury filter was characterized by combining experimental measurements and proper modeling. The Rayleigh-Brillouin spectral profiles were calculated employing the S6 model. Quantitative interpretations of two-dimensional FRS signals were performed in both premixed and diffusion flames. The temperature values obtained were in good agreement with adiabatic calculations and earlier measurements.     

天然气以及大气中微量汞的监测方法的研究

本研究了天然气以及大气中微量汞的监测方法：以高精密度的冷原子吸收光谱法和便携式塞曼效应原子吸收光谱法为基础,建立了完整的大面积网络快速实时监测系统。     

Molecular Structure and Electronic Spectra of CoS under the Radiation Fields

We optimized the ground-state stable configuration of CoS molecule in different external radiation fields (0-0.04 atomic units (a.u.)) at the basis set level of 6-311G++ (d, p) using the B3LYP density functional theory. On this basis, the molecular structure, total energy, energy gap, and the intensities of infrared ray (IR) spectra, Raman spectra, and ultraviolet-visible (UV-Vis) absorption spectra of CoS molecule were computed using the same method. The results showed that the molecular structure changed greatly under the effect of the external radiation fields and had significant dependency on the radiation fields. The total energy of CoS molecule grew slightly at first and then significantly decreased in a monotonous manner. The bond length, dipole moment, and energy gap of the molecule all reduced at first and then increased, with the turning point all at F=0.025 a.u. of the radiation field. The absorption peak of IR spectra and Raman optical activity both had maximums at F=0.03 a.u. with significant red shift. In the external radiation field of F=0.030 a.u., the absorption wavelength of the UV-Vis absorption spectra showed large blue shift, and a strong absorption peak was observed.     

原子吸收法测定白酒中铅和锰的方法改进

目的:本文以简化操作步骤,改进实验方法为目的,着重研究利用原子吸收光谱法直接测定白酒中的铅和锰。方法:直接对样品进行稀释,用火焰原子吸收法测定锰。以磷酸氢二铵为基体改进剂,用石墨炉原子吸收光谱法测定铅。结果:该方法操作简单快速,减少了试剂用量,而且精密度和准确度都能满足实验要求。结论:该方法是可行的,值得推广使用。     

Development of a new holographic method with resonant X-ray scattering

Complex X-ray holography (CXH) using resonant scattering is proposed as a new atomic resolution holography method. CXH provides us a solution for the twin-image problem as well as elemental identification in real space. Accurate differences among intensities recorded at several X-ray energies around an absorption edge must be experimentally obtained in the CXH method. Taking into account that the holographic signal is of the order of 0.1% of its background, we find it difficult to carry out using ordinary technique for hologram measurement. Thus, in order to measure holograms with a very good S/N ratio, a sample was cooled about 100 K and fluorescent X-rays were focused on a detector with a cylindrical graphite analyzer in the X-ray fluorescence holography apparatus at SPring-8. Ga fluorescent holograms of GaAs were recorded at energies near the As K absorption edge. A change of holographic oscillations due to the resonant scattering, which is expected from the computer simulation, was firstly observed.     

Epitaxial growth of high quality AlGaAs/GaAs structures on atomically flat GaAs surfaces in deep dielectric windows cleaned using atomic hydrogen

An improved method to grow AlGaAs/GaAs structures on GaAs inside deep dielectric windows (DDWs) is reported. Samples which have undergone patterning and etching to form the DDWs were subjected to atomic hydrogen irradiation generated by a hydrogen cracker cell in a molecular beam epitaxy (MBE) system at a substrate temperature of approximately 450 °C and hydrogen background pressure of 10⁻⁶ torr. AlGaAs/GaAs quantum well structures of different well widths grown on GaAs inside the DDWs pre-cleaned using atomic hydrogen showed two to five times improvement in photoluminescence (PL) linewidth compared to samples with area inside the DDWs subjected to thermal oxide desorption at 580 °C. The GaAs surface inside the DDWs cleaned using atomic hydrogen is atomically flat surface with surface roughness of 0.252 nm. This value is five times lower compared to that in the sample subjected to thermal oxide desorption. The use of atomic hydrogen is shown to be effective for cleaning the GaAs surface inside the DDWs, making it possible for MBE re-growth of high quality AlGaAs/GaAs structures for optoelectronic integration.     

石墨炉原子吸收分光光度法测定水中硒的不确定度评定

参照JJF 1059-1999<测量不确定度评定与表示>的技术规范,通过对石墨炉原子吸收分光光度法测定水质硒标准样品过程的分析,阐明了硒不确定度的评定步骤和评定方法。     

X-Ray absorption study of CeO2 and Ce/V mixed oxide thin films obtained by sol-gel deposition

CeO₂ and Ce/V mixed oxide thin films prepared by sol-gel deposition and annealed in an air or argon atmosphere have been studied by chronocoulometry and by XAFS (X-ray absorption fine structure). Multielectron photoexcitations (MPE), well known to pervade XAFS spectra of Ce making the analysis of structural parameters unreliable, are removed with the help of the atomic absorption background, determined on simple Ce compounds. Distinct MPE estimates for Ce³⁺ and Ce⁴⁺ ions are used. In the analysis of the recovered pure XAFS signal, the degree of disorder is found to depend on the Ce/V molar ratio and on the heating atmosphere. The disorder correlates with charge capacity of films, both increasing with vanadium content and V⁴⁺/V⁵⁺ molar ratio.     

Kinetics of hydrogen uptake for getter materials

This paper studies the kinetics of hydrogen absorption for a non-evaporable getter material, and presents a basic gettering model. Hydrogen uptake takes three processes in this model: molecular dissociated chemisorption on the surface, atomic penetration from the surface to the bulk, and diffusion in the body. For low hydrogen bulk concentration a lattice-gas model is adopted to describe the diffusion behaviour of hydrogen in the bulk. The exact analytical solutions are given for the pumping hydrogen by solving rate equations of these three processes simultaneously. The influences of some factors on the hydrogen absorption rate are also discussed. The theoretical calculations are in good agreement with the experiments performed with a Zr-Al (16%) getter and a Zr film on the Mo substrate.     

Comparative structural and electronic studies of hydrogen interaction with isolated versus ordered silicon nanoribbons grown on Ag(110)

We have investigated the geometry and electronic structure of two different types of self-aligned silicon nanoribbons (SiNRs), forming either isolated SiNRs or a self-assembled 5?×?2/5?×?4 grating on an Ag(110) substrate, by scanning tunnelling microscopy and high resolution x-ray photoelectron spectroscopy. At room temperature we further adsorb on these SiNRs either atomic or molecular hydrogen. The hydrogen absorption process and hydrogenation mechanism are similar for isolated or 5?×?2/5?×?4 ordered SiNRs and are not site selective; the main difference arises from the fact that the isolated SiNRs are more easily attacked and destroyed faster. In fact, atomic hydrogen strongly interacts with any Si atoms, modifying their structural and electronic properties, while molecular hydrogen has first to dissociate. Hydrogen finally etches the Si nanoribbons and their complete removal from the Ag(110) surface could eventually be expected.     

Long path atomic/ionic absorption spectrometry in an inductively coupled plasma

A novel approach was taken to increase the atomic/ionic absorption path length in an inductively coupled plasma (ICP) by using a water-cooled quartz "T-shaped" bonnet. Atomic and ionic absorption spectrometry was performed utilizing a continuum source and line sources. Absorption spectra of synthetic multielement solutions were collected with a photodiode array. Sample introduction into the ICP was accomplished with an ultrasonic nebulizer. To prevent the bonnet from cracking, low radio frequency powers were utilized (i.e., 400-600 W). Plasma diagnostics were performed to study the plasma temperature and electron number density within the "T-shaped" bonnet. Analytical figures of merit were found to be better than those obtained from previous work attempted with inductively coupled plasma atomic absorption spectroscopy and approaching that of flame atomic absorption spectroscopy.     

UV vapor generation for determination of selenium by heated quartz tube atomic absorption spectrometry

A new vapor generation technique utilizing UV irradiation coupled with atomic absorption for the determination of selenium in aqueous solutions is described. In the presence of low molecular weight organic acid solutions, inorganic selenium(IV) is converted by UV irradiation to volatile selenium species, which are then rapidly transported to a heated quartz tube atomizer for detection by atomic absorption spectrometry. Optimum conditions for photochemical vapor generation and interferences from concomitant elements were investigated. Identification of the volatile products using cryotrapping GC/MS analysis revealed that inorganic selenium(IV) is converted to volatile selenium hydride, selenium carbonyl, dimethyl selenide, and diethyl selenide in the presence of formic, acetic, propionic, and malonic acids, respectively. In acetic acid solution, the efficiency of generation was estimated to be 50 +/- 10%. No interference from Ni(2+) and Co(2+) at concentrations of 500 and 100 mg L(-)(1), respectively, was evident. A detection limit of 2.5 microg L(-)(1) and a relative sensitivity of 1.2 microg L(-)(1) (1% absorption) with a precision of 1.2% (RSD, n = 11) at 50 microg L(-)(1) were obtained.