Theoretical prediction on vibrational spectra of [Ar…Ar-H]~+

As a special substance between isolated molecules and condensed phase, clusters have drawn more and more attention by theoreticians and experimentalists. The protonated rare gas cluster is one kind of simplest clusters, which can be looked on as the simplest solution composed of the simplest solute, proton, and the simplest solvent, rare gas. The study on such a system can help us to know more about the complex condensed matter. However, the information for the molecular properties of protonat…     

Quantitative surface analysis by Auger and x-ray photoelectron spectroscopy

Recent developments in quantitative surface analysis by Auger (AES) and x-ray photoelectron (XPS) spectroscopies are reviewed and problems relating to a more accurate quantitative interpretation of AES/XPS experimental data are discussed. Special attention is paid to consideration of elementary physical processes involved and influence of multiple scattering effects on signal line intensities. In particular, the major features of core-shell ionization by electron impact, Auger transitions and photoionization are considered qualitatively and rigorous approaches used to calculate the respective transition probabilities are analysed. It is shown that, in amorphous and polycrystalline targets, incoherent scattering of primary and signal Auger and photoelectrons can be described by solving analytically a kinetic equation with appropriate boundary conditions. The analytical results for the angular and energy distribution, the mean escape depth, and the escape probability as a function of depth of origin of signal electrons as well as that for the backscattering factor in AES are in good agreement with the corresponding Mote Carlo simulation data. Methods for inelastic background subtraction, surface composition determination and depth-profile reconstructions by angle-resolved AES/XPS are discussed. Examples of novel techniques based on x-ray induced photoemission are considered.     

Temperature regulation for thermal analysis under microwave radiation

In a microwave study a program was designed for thermal regulation. This software allows different types of regulations: P, PI, PD or PID (proportional integration derivation). Results obtained with PID and PI regulation for different previous linear heating schedules (1 deg·s^?1 and 0.15 deg·s^?1) imposed on a polymer sample (DGEBA/3DCM) up to 280°C and more are reported. Mathematical resolution of thermal laws applied to the sample permits the regulation constants (T _i,T _d andG _s) to be linked to the physical features of the polymer. A method used to calculate: the reflexion constant of the wave on the polymer, ρ and the diminution factor, α is presented.     

Characterization of the Surface Electrode Reaction in the Presence of Uniform Interaction: The Case of Mo(VI) Reduction in the Presence of Phenanthroline and an Excess of Fulvic Acids

Surface electrode reactions involving lateral uniform interactions between adsorbed species is studied by means of square‐wave voltammetry (SWV). Interactions are represented by the interaction product aΘ, were a is the Frumkin interaction parameter (a is positive for attraction and negative for repulsion forces) and Θ is the surface coverage. The properties of the SW voltammetric response enable detection of interactions and recognition of the type of interaction forces by a simple procedure. The influence of the interactions on the apparent electrochemical reversibility of the surface electrode reaction is studied in detail. Utilizing “quasireversible maximum” the simple methodology for estimation of the standard redox rate constant without knowing the exact value of the interaction product aΘ is developed. Theoretical predictions are illustrated and confirmed by experiments with Mo(VI) in the presence of phenantroline and an excess of fulvic acids.     

Investigation of the thermophysical properties of polymers by the temperature wave technique

The technique of temperature waves to measure the complex thermophysical characteristics of materials has been proposed. The relations for the moduli and arguments of these characteristics for the case of plane temperature waves have been calculated. The temperature dependences of the moduli and arguments of complex thermophysical characteristics of polyvinylacetate (PVAc) at different frequencies and also the temperature dependences of its vibrational and configurational heat capacities have been determined. It has been shown that the vibrational heat capacity of PVAc in the region of softening grows sharply and its configurational heat capacity goes through a peak. The segmental mobility has been found to affect the heat transfer in the polymer in an ambivalent way causing both a decrease and increase of thermal conductivity.

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Zusammenfassung Zur Bestimmung der komplexen thermophysischen Eigenschaften von Stoffen wurde eine Temperaturwellentechnik vorgeschlagen. Für den Fall zweidimensionaler Temperatur-wellen wurden die Verhältnisse von Moduli und Argumenten dieser Eigenschaften berechnet. Die Temperaturabhängigkeit von Moduli und Argumenten der komplexen thermophysischen Eigen-schaften von Polyvinylacetat (PVAc) bei verschiedenen Frequenzen und auch die Temperatur-abhängigkeit seiner Vibrations- und Konfigurations-Wärmekapazitäten wurden bestimmt. Es wurde gezeigt, daß die Vibrations-Wärmekapazität von PVAc im Erweichungsbereich scharf zunimmt und die Konfigurations-Wärmekapazität durch einen Peak geht. Man fand, daß die Segment-Mobilität den Wärmetransport im Polymer auf eine ambivalente Weise beeinflußt, in dem die Wärmeleit-fähigkeit entweder gesenkt oder angehoben wird.

     

示波极谱法直接测定水中超痕量钨

本文对钨—溴邻苯三酚红极谱催化波进行了研究,发现体系中加入四乙基碘化铵后,极谱渡高明显增加,体系的稳定性显著提高,检出限达1.8×10~(-11)mol/L。确定了最佳条件,拟定了不经分离富集直接测定水中痕量钨的方法。此外还对极谱波性质进行了探讨,证明该极谱波为配合物吸附催化氢波,讨论了阳离子表面活性物质对催化氢波的作用机理。     

锰（Ⅱ）—邻菲口罗啉配合物极谱吸附波及其应用

在ｐＨ９．５ＮＨ３ＮＨ４Ｃｌ缓冲溶液中，Ｍｎ（Ⅱ）与邻菲口罗啉形成的配合物在－１．３６Ｖ（ｖｓ．ＳＣＥ）处产生一灵敏的吸附波，一阶导数峰电流与Ｍｎ（Ⅱ）浓度在５×１０－８５×１０－６ｍｏｌ／Ｌ范围内呈线性关系，检出限为２×１０－８ｍｏｌ／Ｌ对极谱性质及反应机理进行了研究，用该法测定了大豆和茶叶中的微量锰，结果满意     

Utilization of a Copper Solid Amalgam Electrode for the Analytical Determination of Atrazine

A copper solid amalgam electrode was prepared and used for the voltammetric determination of atrazine in natural water samples by square wave voltammetry. This electrode is a convenient substitute for the hanging mercury electrode since it is selective, sensitive, reliable and inexpensive and presents low toxicity characteristic. The detection limit of atrazine obtained in pure water (laboratory samples) was shown to be lower than the maximum limit of residue established for natural water by the Brazilian Environmental Agency. The relative standard deviation for 10 different measurements was found to be only 3.98% in solutions containing 8.16×10^?6 mol L^?1 of atrazine. In polluted stream water samples, the recovery measurements were approximately 70.00%, sustaining the applicability of the proposed methodology to the analysis of atrazine in such matrices.