Electrothermal atomization of calcium and strontium in a molybdenum micro-tube

The excitation and ionization of calcium and strontium in a molybdenum micro-tube atomizer and their use in atomic-absorption spectrometry are described. Increasing hydrogen flow led to complex calcium atomization profiles for absorption measurements, but decreasing hydrogen flow resulted in higher atomic emission. Ionization of calcium and its suppression by potassium were also observed. Strontium was measured effectively by atomic absorption because of the higher sensitivity. Increasing hydrogen flow resulted in a lower atomization temperature and higher absorption for strontium, while decreasing hydrogen flow resulted in higher atomic emission. No interference from 100-fold amounts of magnesium, calcium and sodium was found for atomization of strontium, but 100-fold amounts of aluminium shifted the peak temperature for strontium though with no variation of appearance temperature and peak absorption. A small shift in peak temperature was observed for strontium in the presence of 100-fold amounts of phosphate.     

Photoelectron angular distributions of Cu,Ag, Pt and Au samples: experiments and simulations

Angular distributions of photoelectrons emitted from semi‐infinite Cu, Ag, Pt and Au specimens have been measured for off‐normal emission angles in the range between 20 and 70° with a Thermo Theta Probe electron spectrometer. Experimental peak intensities for peaks of atomic subshells observable in the spectra were compared with results of simulations using the NIST Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) that takes into account the effects of (i) anisotropy of the photoelectric cross‐section; (ii) elastic scattering of the photoelectrons; and (iii) the finite solid angle of the detector. In addition, a separate correction was made to the simulated intensities for the effects of surface excitations. The combined influence of these effects was found to significantly affect the angular distributions. Furthermore, it was found that ratios of the calculated peak intensities of the observed subshells for a particular material to the measured intensities deviate from unity by typically less than 1% after corrections for multiple inelastic scattering and surface excitations. Copyright © 2010 John Wiley & Sons, Ltd.     

Graphite furnace atomic emission spectrometry with platform atomization

The effect of inserting a pyrolytic graphite platform into a heated graphite atomizer HGA-2100 on the atomic emission of Mo, V, Al, Ni, Cu, Cr, Mn, Zn and Cd has been studied. A comparison of calibration curves obtained with and without the use of the platform showed that although the linear dynamic range is diminished by the use of the platform, atomic emission intensities are increased by as much as 23.5 times in the most favourable case (Al) studied.Whereas no detectable net emission signal could be obtained from 5.0 × 10^?9 kg of Zn and Cd atomized from the graphite tube wall, atomization and emission from the platform yielded limits of detection: 2.7 × 10^?12 kg for Zn and 4.0 × 10^?12 kg for Cd.     

石墨管内被测原子间的平衡关系

本文探讨了石墨管内被测原子间的平衡关系,从理论上推导了基态原子数与吸光度之间的系数β,计算了部分元素的理论特征量N值.     

Quantification of surface roughness effect on elastically backscattered electrons

Electron inelastic mean free path can be obtained from a measured elastic peak electron spectroscopy spectrum combined with a Monte Carlo simulation. It is thus necessary to know the influence of various experimental factors to the measured and calculated results. This work investigates the effect of the surface roughness or the surface topography on the intensity of the elastic peak. A Monte Carlo simulation, by taking into account of realistic surface roughness for both Gaussian and non‐Gaussian type rough surfaces experimentally prepared, has been employed to study the surface topography effect. The simulations of elastic peak electron spectroscopy were performed for both planar and rough Al and Cu surfaces and for varied primary energies ranging from 200 to 2000 eV. To quantify the surface roughness effect, the surface roughness parameter is introduced according to the ratio of elastic peak intensities between a rough surface and an ideal planar surface. Simulation results have shown that surface roughness parameter is important in a certain range of emission angle and particularly for large emission angles. For grazing emission, the elastic peak intensity can be largely enhanced by roughness even at nanometer scale. Copyright © 2014 John Wiley & Sons, Ltd.     

pH对玫瑰红色素紫外和荧光光谱的影响

玫瑰是蔷薇科蔷薇属落叶丛生灌木,品种繁多,其花色、香、形具美,有极高的观赏和经济价值,我国玫瑰资源丰富,古代人们就将玫瑰用于染色、食品和药用等领域,现在玫瑰主要用于商品花卉和提取玫瑰精油.     

Electrothermal atomization from metallic surfaces: Part 3. Some new developments in design and performance of a tungsten-tube atomizer

A new design of a work-head for a tungsten-tube atomizer as well as voltage- and temperature-feedback circuits added to the power supply of a Varian model CRA-63 atomizer are described. The importance of rapid, temperature-controlled heating of the atomizer is shown. The effect of heating rate (0.5–20 K ms^-1) on the analytical signal of many elements is investigated; experimental atomization and residence times and peak absorbance values are evaluated. The analytical performance of the tungsten-tube atomizer is tested for elements of different volatilities.     

Cross-correlation masks for automatic detection of spectral information

Cross-correlation masks based on spectral intensities and binary spectral peak positions are evaluated for detection and quantitation of atomic emission spectra. The inductively coupled plasma emission spectra of nickel and vanadium as acquired with a photodiode array spectrometer were utilized to test and illustrate the cross-correlation procedures.     

Electrothermal Atomization Atomic Absorption Spectrometry with Platinum Tube Atomizer in Air

Abstract

An electrothermal atomization method of atomic absorption spectrometry using a platinum tube atomizer in air is described. The atomizer consists of 0.025 mm-walled platinum tube and two supports. The remarkable merit of the platinum atomizer is the stability in air, when heated. This paper describes the improved performance for volatile elements like alkalimetals. Detection limits and characteristic mass are calculated for 7 elements and compared with literature values. The platinum atomizer can be used with a simple, effective and relatively low-cost atomic absorption spectrometer for routine in situ analysis.     

Molecular orbital interpretation of X-ray emission spectra of ClCN and ONCl

Ab initio as well as semi-empirical SCF MO calculations are presented for ClCN and ONCl. The relative intensities for Cl Kβ emission in the two molecules were calculated. The calculated spectra from the ab initio wavefunctions are in excellent agreement with experiments.     

Electronic and vibrational spectra of some rare earth trifluoromethanesulfonates crystals

Nanocrystalline ZnO powders have been synthesized by a low temperature solution combustion method. The photoluminescence (PL) spectrum of as-formed and heat treated ZnO shows strong violet (402, 421, 437, 485 nm) and weak green (520 nm) emission peaks respectively. The PL intensities of defect related emission bands decrease with calcinations temperature indicating the decrease of Zn(i) and V(o)(+) caused by the chemisorptions of oxygen. The results are correlated with the electron paramagnetic resonance (EPR) studies. Thermoluminescence (TL) glow curves of gamma irradiated ZnO nanoparticles exhibit a single broad glow peak at ～343°C. This can be attributed to the recombination of charge carriers released from the surface states associated with oxygen defects, mainly interstitial oxygen ion centers. The trapping parameters of ZnO irradiated with various γ-doses are calculated using peak shape method. It is observed that the glow peak intensity increases with increase of gamma dose without changing glow curve shape. These two characteristic properties such as TL intensity increases with gamma dose and simple glow curve structure is an indication that the synthesized ZnO nanoparticles might be used as good TL dosimeter for high temperature application.     

White light emission from nano-fibrous ZnO thin films/porous silicon nanocomposite

Nanocomposites composed of nano-fibrous ZnO thin films and porous silicon (PS) were prepared and examined by atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy, and photoluminescence (PL) to investigate their structural and optical properties. PS, consisting of irregular and random nanosized-pores, was prepared by electrochemical anodization. The nano-fibrous ZnO thin films were grown on PS by the sol-gel spin-coating method. The texture coefficient (TC _(hkl)) of the nano-fibrous ZnO thin films was calculated to determine the preferred orientation. The nano-fibrous ZnO thin films were grown with a c-axis preferred orientation. The residual stress in the films was reduced in the case of PS. The observed broad PL emission peak from 460 to 598 nm was attributed to coupled emission from ZnO to PS. The results show that white light luminescence with blue, green, and red emission peaks having highly uniform intensities can be obtained from the nanocomposite via a relatively simple and low-cost sol-gel spin-coating method.     

Discriminating detection between Mg2+ and Ca2+ by fluorescent signal from anthracene aromatic amide moiety

Novel fluorescent reagents 1 and 2 were synthesized. In the absence of metal ions, the fluorescence emissions of these compounds were quite weak, but their intensities were much greater in the presence of alkaline earth metal ions. The peak shape and maximum wavelength of the emission of the complex with Mg2+ differed from those of Ca2+ and other alkaline earth metal ions. The peak wavelength difference was 30 nm.     

Determination of some rare-earth elements by plasma-jet emission spectrometry

The effects of a magnetic field on spectral intensities in plasma-jet spectrometry were examined, and detection limits for rare-earth elements were calculated. Plasma-jet emission spectrometry was applied to the determination of lanthanum, yttrium and gadolinium in a monazite sample from which thorium had been separated. A standard addition method was used in order to improve accuracy, and the internal standard and background compensation method was applied to measurements of spectral line intensities to achieve good precision. The coefficient of variation was 1.51% for 50 μg La ml^?1.     

Transverse heated filter atomizer for electrothermal atomic absorption spectrometry

The filter furnace atomization concept was applied for the transverse heated atomizer. A graphite filter with graphite fiber reeled onto it was inserted into the tube of the standard transverse heated graphite atomizer (THGA) in the place of the platform. Automatic plugging of the sampling hole was applied during the atomization stage. The performance of the filter atomizer (THFA), compared with the THGA, was tested for the determination of Ag, As, Au, Bi, Cd, Cu, Ga, In, Mn, Pb, Sb, Se and Tl. The analytical performances of the THFA displayed some advantages in comparison with the THGA. The sampling volume varied in the range of 5–90 μl, while drying time for any volume was less than half of that used for the THGA. Owing to the reduced diameter of the analytical zone (2 mm) along the filter axis, a sensitivity improvement was observed for all elements, 1.3–2.8-fold without plugging and 4.3–4.8-fold for Bi, Cd, Pb and Tl with plugging of the dosing hole. An increased peak width (by two to five times for the elements tested) limited the determination of less-volatile metals. The intensity of light decreased by 20–30% in comparison with the THGA. Taking into account the sensitivity, sampling volume, light loss and signal width, the calculated gain in relative detection limit is substantial (about 2.5–7 times) only for volatile elements when the plugging is applied. The pyrolysis temperatures for Ag, As, Au, Cd, Cu and Se in the THFA without addition of modifier were by 200–600°C higher than in the THGA using Pd/Mg modifier. The lifetime of THFA tubes was similar to that of THGA tubes.     

Spatial characterization of analyte emission and excitation temperature in an inductively coupled plasma

Vertical, lateral and radial profiles of analyte emission in an inductively coupled plasma have been measured using photodiode array spatial profiling spectrometers. These profiles have been measured for both neutral atom and ionic lines of several elements. Neutral atom lines can be sub-divided into two basic groups on the basis of their vertical spatial emission characteristics. One group in which the peak vertical position of emission correlates positively with normal temperature and a second group in which the peak vertical position of emission correlates negatively with normal temperature. Utilizing radially resolved emission intensities and vertical and radial profiles of neutral atom excitation temperature, the caracteristic emission patterns of both groups of neutral atom lines can be explained. Analyte ionic line spatial emission characteristics, both vertically and radially, are shown to be relatively species independent and radial emission intensity ratio maps of ionic and neutral atom lines of the same element are presented that indicate the potential importance of plasma boundary regions as regions of major non-LTE behavior.     

Shake-up peak positions and intensities by many-body theory methods

The valence shell X-ray photoelectron spectrum of N₂ is calculated using the equations-of-motion—Green's function method. The inclusion of shake-up basis operator configurations in the primary operator space along with the simple ionization operator configurations allows for the calculation of shake-up peak positions on an equal footing with the simple ionization energies. The important shake-up basis operator configurations are identified using configuration selection techniques similar to those which have been successfully employed in large scale configuration interaction problems, thus minimizing the size of the matrices to be diagonalized. The relative peak intensities are calculated within the plane wave approximation. The intensity equations are analyzed indicating that the relative peak intensities are more sensitive to ground state correlation effects than the peak positions. Modifications of the theory to improve the calculations of shake-up energies are discussed.     

Investigations of stimulated emission onB-A lines in CO

Stimulated emission has been studied in the decay of the two-photon populatedB ¹Σ state in CO. Radiative lifetimes, quenching rates, two-photon absorption and ionization cross-sections were also measured. Rate equations for the involved energy levels have been solved and stimulated emission intensities have been calculated.     

Comparison of keV N2(+*)/He and N2(+*)/Ar collisions by emission spectroscopy and theory

Collision-induced emission spectra from 190-1020 nm were obtained for N 2 (+*)/Ar collisions at laboratory frame collision energies from 2 to 8 keV. The relative emission intensities of N 2 (+*), N (+), and N (*) are independent of the ion translational energy within the studied energy range, supporting the curve-crossing mechanism for collisional excitation. The role of the target gas in keV N 2 (+*)/He and N 2 (+*)/Ar collisions was investigated by both emission spectroscopy and theoretical calculations. Adiabatic potential energy surfaces calculated at the CISD/6-311+G(2df) level of theory for N 2 (+*)/He and N 2 (+*)/Ar collisions indicate that excitation to the A (2)Pi u and B (2)Sigma u (+) states involves curve-crossing first to the C (2)Sigma u (+) state, and the difference in N 2 (+*) emission intensities from the two systems can be accounted for by the slope difference at the crossing points based on the Landau-Zener curve-crossing model.     

KMgF3 及KMgF3∶Eu2+晶体的射线辐照效应

KMgF3∶Eu晶体中Eu3+→Eu2+的转换率在低浓度掺杂时接近100%, 完全转换的饱和掺杂摩尔分数为0.29%. 实验条件下, KMgF3晶体的X射线1 h辐照损伤可在约100 h后恢复; KMgF3∶Eu2+晶体经X射线辐照后, 360 nm锐峰发射强度略有降低. 不同剂量的γ射线辐照, KMgF3晶体热释光曲线的各个温度峰强度变化明显不同, 即使小剂量辐照, 造成的损伤也较难恢复, 如γ射线辐照剂量为103 Gy时, 辐照损伤的恢复时间约需30 d. KMgF3∶Eu2+晶体360 nm锐峰发射强度随γ射线辐照剂量增大而呈线性降低.