Spatial and temporal probing of a laser-induced plasma plume by cavity ringdown spectroscopy

The laser-induced plasma plume of a Ti target in vacuum is probed by the technique of cavity ringdown spectroscopy. A model is developed to perform a forward convolution of atomic absorption line profile measurements. The model accounts for laser-induced plasma characteristics such as anisotropy of the plume and velocity distributions of the ablated particles as well as of the cavity ringdown features such as geometry and time selectivity. The absorption lineshapes of atomic transitions are calculated and discussed for given sets of parameters. Calculated line profiles are fitted to experimental line profiles obtained from nanosecond-laser ablation of the target and provide data about the plume dynamics.     

Evaluation of a hydride generation-atomic fluorescence system for the determination of arsenic using a dielectric barrier discharge atomizer

A new atomizer based on atmospheric pressure dielectric barrier discharge (DBD) plasma was specially designed for atomic fluorescence spectrometry (AFS) in order to be applied to the measurement of arsenic. The characteristics of the DBD atomizer and the effects of different parameters (power, discharge gas, gas flow rate, and KBH₄ concentration) were discussed in the paper. The DBD atomizer shows the following features: (1) low operation temperature (between 44 and 70 °C, depending on the operation conditions); (2) low power consumption; (3) operation at atmospheric pressure. The detection limit of As(III) using hydride generation (HG) with the proposed DBD-AFS was 0.04 μg L⁻¹. The analytical results obtained by the present method for total arsenic in reference materials, orchard leaves (SRM 1571) and water samples GBW(E) 080390, agree well with the certified values. The present HG-DBD-AFS is more sensitive and reliable for the determination of arsenic. It is a very promising technique allowing for field arsenic analysis based on atomic spectrometry.     

Preparation and nonlinear optical properties of novel Y-type polyesters with highly enhanced thermal stability of second harmonic generation

3,4-Di-(2′-hydroxyethoxy)benzylidenemalononitrile (3) was prepared and condensed with terephthaloyl chloride and adipoyl chloride to yield novel Y-type polyesters (4-5) containing 3,4-dioxybenzylidenemalononitrile groups as NLO-chromophores, which constituted parts of the polymer main-chains. The resulting polymers 4-5 are soluble in common organic solvents such as acetone and N,N-dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis with glass-transition temperatures obtained from differential scanning calorimetry in the range 89-91 °C. The second harmonic generation (SHG) coefficients (d₃₃) of poled polymer films at the 1064 nm fundamental wavelength were around 2.47 pm/V. The dipole alignment exhibited high thermal stability even at 10 °C higher than T_g, and there is no SHG decay below 100 °C due to the partial main-chain character of polymer structure, which is acceptable for NLO device applications.     

Investigation of chromium(III) acetylacetonate as a calibration reference material for atomic absorption spectroscopy

It is shown that chromium(III) acetylacetonate meets the requirements of calibration reference materials: it is homogeneous, soluble in water and organic solvents, and its solutions are stable. Chromium(III) acetylacetonate has been successfully used as a calibration reference material in the analysis of chromium in iron-base alloys. The procedure involves chromium acetylacetonate extraction using methyl isobutyl ketone followed by direct atomic absorption analysis of the organic extract. The detection limit of the procedure is 10 ng g⁻¹. Correspondence: Konstantin Belikov, State Scientific Institution “Institute for Single Crystals” of the National Academy of Sciences of Ukraine, Kharkov, Ukraine     

几种(C^N)PtIIQ型配合物的电子结构和紫外-可见吸收光谱

在B3LYP/LANL2DZ水平上优化了三种(C^N)PtIIQ 型配合物基态的几何结构, 进行了频率计算, 并采用含时密度泛函(TD-DFT)方法结合极化连续体模型(PCM)计算了目标配合物在CH2Cl2溶液中的电子结构和紫外-可见吸收光谱. 计算值与文献报道值相似. 计算结果表明这三种(C^N)PtIIQ型配合物在可见光区都有强度较大而且宽的吸收峰, 它们的最低能量吸收峰的跃迁具有ILCT(配体内部电荷转移)和部分MLCT(金属向配体的电荷转移)的特征, 不同于PtIIQ2型配合物在多数情况下表现出的ILCT的跃迁性质.     

几种（C^N）Pt^ⅡQ 型配合物的电子结构和紫外-可见吸收光谱

在B3LYP/LANL2DZ水平上优化了三种(C^N)PtⅡQ型配合物基态的几何结构,进行了频率计算,并采用含时密度泛函(TD-DFr)方法结合极化连续体模型(PCM)计算了目标配合物在CHCl2溶液中的电子结构和紫外.可见吸收光谱.计算值与文献报道值相似.计算结果表明这三种(C^N)PtⅡQ型配合物在可见光区都有强度较大而且宽的吸收峰,它们的最低能量吸收峰的跃迁具有ILCT(配体内部电荷转移)和部分MLCT(金属向配体的电荷转移)的特征,不同于PtⅡQ2型配合物在多数情况下表现出的ILCT的跃迁性质.     

偏硼酸锂-四硼酸锂熔融-电感耦合等离子体原子发射光谱(ICP-AES)法测定石膏中多组分含量

石膏在我国储量丰富,应用广泛,快速准确分析其成分含量对石膏资源的综合利用具有重要意义。针对酸溶法无法测定SiO2,碱熔法无法测定K2O、Na2O的问题,本文建立一种偏硼酸锂-四硼酸锂熔融-电感耦合等离子体发射光谱法同时测定石膏中CaO、SO3、Al2O3、Fe2O3、MgO、TiO2、K2O、Na2O、SiO2含量。实验优化了熔剂用量、熔融温度,结果表明采用试样与偏硼酸锂-四硼酸锂混合熔剂质量比例1：5,在铂金坩埚中1000 ℃熔融10 min,在超声条件下,于50 mL 10 %盐酸中浸取熔融物,能够有效分解试样而浸取待测组分。向标准溶液系列中加入偏硼酸锂-四硼酸锂-盐酸基体溶液以消除基体对测试结果的影响。各待测组分的校准曲线的相关性系数均大于0.9990,方法检出限在3~292 μg/g范围内;采用实验方法分别对国家一级标准物质GBW03109a、GBW03110和实际样品进行测定,标准物质的5次平行测试的相对标准偏差在0.14 %~8.86 %之间,测定结果的相对误差在0.03~8.75 %之间,测试结果与标准值无显著性差异;实际样品中各成分测定值的RSD（n=5）为0.24~8.80 %。该方法操作简单、准确度高、精密度好、检出限低,可以同时测定石膏中的多组分含量,能够为石膏资源综合利用调查评价提供一定的技术支撑 。     

Activation-induced layered structure in NiCoAl by atomic modulation for energy storage application

The surface activation of alloys favors their electrochemical interactions, ion diffusivity, and the rapid kinetics of ions and electrons, leading to the formation of self-supported layered double hydroxides (LDHs) in them. However, the formation of LDHs at different depths in the alloy upon activation, their electronic/atomic structures, and their electrochemical charge storage mechanism, have not been thoroughly explored. Herein, Ni ion-substituted CoAl alloys are prepared by arc melting and activated by KOH electrolyte, which is responsible for the modulation of the atomic configuration as confirmed by XRD. Raman depth mapping demonstrates how the LDHs vary with depth upon activation and that the octahedral and tetrahedral symmetry sites of CoO and Co₃O₄ are responsible for the formation of the layered structures of CoOOH and Co(OH)₂, respectively. The activated Ni₁₀Co₈₅Al₅ has a superior volumetric capacitance of 4.15 F/cm³ at 0.5 mA/g, which is 38.6 times that of an unactivated one, and excellent cyclic stability up to 5000 cycles, and a voltage of 0.54 V generated from a fabricated supercapacitor cell. X-ray Absorption Spectroscopy (XAS) analysis indicates greater charge transfer by Co than by Ni and the modulation of the local atomic structures facilitates electrochemical charge storage in Ni₁₀Co₈₅Al₅. This work presents an easy route for the development of advanced LDHs, and the mechanism of electrochemical charge storage in them.     

Cooperative single-photon subradiant states in a three-dimensional atomic array

We propose a complete superradiant and subradiant states that can be manipulated and prepared in a three-dimensional atomic array. These subradiant states can be realized by absorbing a single photon and imprinting the spatially-dependent phases on the atomic system. We find that the collective decay rates and associated cooperative Lamb shifts are highly dependent on the phases we manage to imprint, and the subradiant state of long lifetime can be found for various lattice spacings and atom numbers. We also investigate both optically thin and thick atomic arrays, which can serve for systematic studies of super- and sub-radiance. Our proposal offers an alternative scheme for quantum memory of light in a three-dimensional array of two-level atoms, which is applicable and potentially advantageous in quantum information processing.     

Absorption of sound at a surface exposed to flow and temperature gradients

In noise abatement using porous or fibrous materials, accurate determination of the surface impedance representing the absorber is decisive for simulation quality. The presence of grazing flow and non-homogeneous ambient temperature influence the reaction of the absorber and may suitably be included in a modified “effective” surface impedance. In this paper, this approach is applied to a generic case representative for the engine bay of a heavy truck, where porous shields suppress the radiated noise, e.g. during a pass-by noise test. The change in the absorption is determined numerically by solving the wave propagation through a layer of varying temperature and flow adjacent to the impedance surface for different angles of incidence. The study shows significant impact of both flow and temperature, especially for materials with low absorption. The diffuse field absorption coefficient is also derived and although the effect is less pronounced in this case, it is still important in lower frequencies and in the frequency range typical for IC engine noise. The proposed numerical method is shown to be accurate and efficient for determination of the effective impedance and moreover not limited to thin boundary layers.