The thermal explosion of the detonating mixture is impossible without a chain avalanche

The fundamental regularities of hydrogen/oxygen combustion are considered, which unambiguously indicate the branched chain character of the process at atmospheric pressure. It is noted that, in the general case, the ignition conditions are determined by the competition between chain termination and both chain branching and chain propagation reactions. Some publications ignoring this important point are considered.     

Chemical control of combustion and detonation in carbon oxide and hydrogen mixtures with air

The paper presents data on the control of combustion and detonation in CO and H₂ mixtures with air by small additives. The dependence of the kinetics of combustion and detonation characteristics on the initial mixture composition observed experimentally is in agreement with the predictions of theory taking into account the special features of reaction chains of the combustion of carbon monoxide in the presence of hydrogen-containing impurities. Works ignoring the chain character of the combustion of H₂ and CO are critically reviewed.     

有机硅活性中间体的研究 II. 一些含环丙基的有机硅化合物的合成及其结构

用锂有机物的方法合成了四种含有环丙基有机硅化合物,对上述每种化合物中可能存在着的立体异构进行了分离和和构型测定。     

Rate constants for the reactions of molecular iodine with Cl,SiCl3, and SiH3 at 298 K

Rate constants k₁, k₂, and k₃ have been measured at 298 K by means of a laser photolysis-laser magnetic resonance technique and (or) by a laser photolysis-infrared chemiluminescence detection technique (LMR and IRCL, respectively). \hfill\hbox to 12em{$\rm Cl+I_2\longrightarrow ICl+I;$}\hbox to 8em{$\rm {\it k}_1=(2.5\pm 0.7)\times 10^{-10}(IRCL)$}\hfill(1)\\\hfill\hbox to 12em{}\hbox to 8em{$\rm {\it k}_1=(2.8\pm 0.8)\times 10^{-10}(LMR)$}\hfill \\\hfill\hbox to 12em{$\rm SiCl_3+I_2\longrightarrow SiCl_3I+I;$}\hbox to 8em{$\rm {\it k}_2=(5.8\pm 1.8)\times 10^{-10}(IRCL)$}\hfill (2)\\\hfill\hbox to 12em{$\rm SiH_3+I_2\longrightarrow SiIH_3+I;$}\hbox to 8em{$\rm {\it k}_3=(1.8\pm 0.46)\times 10^{-10}(LMR)$}\hfill (3)\\ As an average of the LMR and IRCL results we offer the value k₁ = (2.7 ± 0.6) × 10⁻¹⁰. Units are cm³ molecule⁻¹ s⁻¹; uncertainties are 2σ including precision and estimated systematic errors. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 25–33, 1997.     

Atomic Absorption Determination of Metals in Soils Using Ultrasonic Sample Preparation

It was shown that ultrasonic treatment accelerates sample preparation of soil extracts from chernozem into different solvents by a factor of 6 to 60. These extracts are used for the atomic absorption determination of soluble species of Cd, Co, Cr, Cu, Ni, Pb, and Zn. The optimum ultrasound parameters (frequency, intensity, and treatment time) were found for preparing soil extracts containing analytes in concentrations required in agrochemical procedures. Different extractants used to extract soluble heavy metals from soils of a standard chernozem type in agrochemical procedures using ultrasonic treatment were classified in accordance with the element nature.     

Narrow resonances of two-photon absorption of super-narrow pulses in a gas

First cw laser oscillation with thresholds below 1 mW was observed for various B¹П_u → X¹ ∑ _g ⁺ transitions of diatomic molecular sodium excited by different argon laser lines in the range of 454–488 nm. For pump powers of 0.5 W output powers up to 3 mW and single-pass gain up to 0.1 cm⁻¹ were obtained. Some properties of the heat pipe laser system are discussed.     

Host-guest interactions at self-assembled monolayers of cyclodextrins on gold

We have developed synthesis routes for the introduction of short and long dialkylsulfides onto the primary side of alpha-, beta-, and gamma-cyclodextrins. Monolayers of these cyclodextrin adsorbates were characterized by electrochemistry, wettability studies, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), and atomic force microscopy (AFM). The differences in thickness and polarity of the outerface of the monolayers were measured by electro-chemistry and wettability studies. On average about 70% of the sulfide moieties were used for binding to the gold, as measured by XPS. Tof-SIMS measurements showed that the cyclodextrin adsorbates adsorb without any bond breakage. AFM measurements revealed for beta-cyclodextrin monolayers a quasi-hexagonal lattice with a lattice constant of 20.6 A, which matches the geometrical size of the adsorbate. The alpha-cyclodextrin and gamma-cyclodextrin monolayers are less ordered. Interactions of the anionic guests 1-anilinonaphthalene-8-sulfonic acid (1,8-ANS) and 2-(p-toluidinyl)naphthalene-6-sulfonic acid (2,6-TNS) and the highly ordered monolayers of heptapodant beta-cyclodextrin adsorbates were studied by surface plasmon resonance (SPR) and electrochemical impedance spectroscopy. The SPR measurements clearly showed interactions between a beta-cyclodextrin monolayer and 1,8-ANS. Electrochemical impedance spectroscopy measurements gave high responses even at low guest concentrations (< or = 5 microM). The association constant for the binding of 1,8-ANS (K = 289,000 +/- 13,000M-1) is considerably higher than the corresponding value in solution. (Partial) methylation of the secondary side of the beta-cyclodextrin strongly decreases the binding.     

The role of the negatively charged (Si3−Si−F2)− complexes in interactions of fluorine with the (111) surface of silicon

We used the AM1 quantum chemical and cluster models to study the mechanism of formation of a SiF₂-like layer and dissociation of the Si−Si bond during the interaction of atomic fluorine with the (111) surface of silicon. It is shown that the negatively charged (Si₃−Si−F₂)⁻ complex with the five-coordinated centered silicon atom plays an important part in these processes. The above complex participates in the interaction of atomic fluorine with silicon to form a SiF₂-like layer and break the subsurface Si−Si bonds without penetration of fluorine atoms into the subsurface silicon layers. Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 1, pp. 14–21, January–February, 1996. Translated by I. Izvekova     

Homogeneous decomposition of formaldehyde induced by a carbon dioxide laser

The homogeneous pyrolysis of formaldehyde has been studied under laser heating. At temperatures of 950–1000 K H₂CO decomposition is shown to be a radical chain reaction. Methanol formation in formaldehyde pyrolysis is a homogeneous reaction.

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. , H₂CO 950–1000° . .

     

Ellipsometric study of the interaction of a germanium monocrystal with bromine

Using an ellipsometric technique, the dynamics of formation of adsorption layers in the process of interaction of bromine with a germanium monocrystal surface has been studied. It is shown that the reaction begins only when the second layer of bromine molecules is formed on the germanium surface. The ellipsometric data are in agreement with the results obtained by kinetic experiments.

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Эллипсометрическим методом исследована динамика адсорбционных заполнений во время химической реакции германия с бромом. Сделан вывод о том, что химическая реакция германия с бромом становится возможной только при адсорбции второго слоя молекул брома. Получено хорошее соответствие между результатами кинетических и эллипсометрических экспериментов.