Monte—Carlo model of the diffusion-limited reaction kinetics in microheterogeneous media. Comparison with the experimental plots of the forward and backward electron phototransfer kinetics on the pore diameter in silica gel

The kinetics of the diffusion-limited decay reaction A + B B was simulated by the Monte—Carlo method on a two-dimensional square lattice with defects presented by randomly distributed sites. The cases were considered where [B] [A] at the random initial distribution (quenching reaction) and [B] = [A] with the initial distribution of the A and B particles on neighboring sites (geminate recombination). The kinetic curves were approximated by the simplest analytical equation [A]/[A]₀ = (1 – )exp[–(kt)^1–h ] + (where k and are constants). The plots of the heterogeneity parameter (h) and time-averaged first-order rate constant vs. concentration of defects (p) or B particles (in the case of quenching) were obtained and compared with similar correlations obtained earlier by the experimental study of the kinetics of forward (quenching reaction) and backward (geminate recombination) electron phototransfer on the surface of different porous silica gels. The experimental plots of h vs. silica gel porosity are in satisfactory agreement with the plots of h vs. p in the model space, if the fraction of volume inaccessible for reactants, calculated from the free silica gel volume, is chosen as the p parameter for silica gel.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1536–1541, August, 2004.     

Three-dimensional quantum dynamics study of vibrational predissociation of HeI_2 van der Waals molecule for low vibrational excitation using the time-dependent wave packet method

Three-dimensional quantum mechanical calculations for vibrational predissociation of HeI2(B) van der Waals molecules are presented using the time-dependent wave packet technique within the golden rule approxima tion.The total and partial decay widths,lifetimes,rates and their dependence on initial vibrational states were obtained for HeI2 at low initial vibrational excited levels.Our calculations show that the calculated tota decay widths,lifetimes and rates agree well with those extrapolated from experimental data available The predicted total decay widths as a function of initial vibrational states exhibit highly nonlinear behavior.The very short propagation time (less.than 1 ps) required in the golden rule wave packet calculation is determined by the duration time of the final state inter-action between the fragments on the vibrationally deexcited adiabatic potential surface.The final state interaction between the fragments is shown to play an important role in determining the final rotational distri     

激光产生的钒硫簇离子的统计分布与结构探讨

以脉冲激光在高真空中溅射钒粉和硫粉的混合物，产生了一系列钒硫原子簇正负离子。根据对其实验记录的激光等离子体质谱进行分析，发现钒硫原子簇的化学键基本上是共价型的，对应于相同钒原子数目的正负离子的相对丰度分别符合于不同形式的对数正态分布。正离子的相对丰度随硫原子数的增加呈对数衰减，由此可以确定各种大小簇合物的簇骼与几何构型；负离子的相对丰度则基本上呈正常的正态分布，说明在簇骼上结合了不同数量硫原子的负离子之结构稳定性大致相近。在实验中还观察到一类硫原子含量较高的簇离子，其中的部分硫原子可能在本身成键形成环状的硫集团后，又与原来的簇骼结合，因而在硫原子数较多时它们的相对丰度符合另一条对数正态分布曲线。     

Metal ion distribution and solubility of Mn1−xCux(HCOO)2 · 2 H2O Mixed Crystals [1–5]

The metal ion distribution on the two metal sites of monoclinic Mn_1?xCu_x(HCOO)₂ · 2(H,D)₂O mixed crystals are studied by infrared and Raman spectroscopic methods. The spectral regions 3 200–3 400 cm^?1 (v_OH), 2 875–2 990 cm^?1 (v_CH), 2 330–2 500 cm^?1 (v_OD of matrix isolated HDO molecules), 1 350–1 400 cm^?1 (symmetric CO₂ stretching modes), 570–950 cm^?1 (H₂O librations), and 490 cm^?1 (M? O lattice modes) are mostly sensitive to the metal ions present. The frequency shifts of these bands with increasing content of copper show that Cu²⁺ prefers the M(1) site, coordinated by HCOO^? only. The strengths of the hydrogen bonds increase on going from manganese to copper formate, due to the increased synergetic effect of Cu²⁺. Solubility and X-ray data of the mixed crystals are included. Irrespective of the same crystal structure, two series of mixed crystals are formed: eutonic area at 0.65 ≥ x ≥ 0.5.     

New hybrid chelating sorbents with grafted 3-aminopropionate groups based on mixed silicon,aluminum, titanium,or zirconium oxides

A series of new hybrid organo-inorganic sorbents with the 3-aminopropionate chelating group was synthesized. The synthesis includes the copolycondensation (sol—gel method) of tetraethoxysilane, 3-aminopropyltriethoxysilane, and several modifiers (MeSi(OEt)₃, EtSi(OEt)₃, Ti(OEt)₄, AlONO₃, ZrOCl₂) followed by carboxyethylation with acrylic acid. The obtained chelating sorbents were characterized by elemental analysis, FT-IR and ¹H NMR spectroscopy, and thermogravimetry. The N-carboxylated sorbents have a higher sorption capacity with respect to metal ions (0.5–0.9 mmol g⁻¹, pH 6.3, NH₄OAc, 20 °C) than the starting sorbents with the primary amino group (0.05–0.2 mmol g⁻¹) and manifest high selectivity for copper(II) ion extraction. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1783–1788, August, 2005.     

Particle-size distribution of polycyclic aromatic hydrocarbons in urban air in southern Spain

The size distribution of polycyclic aromatic hydrocarbons (PAH) was determined for airborne particles from a large city with high vehicular traffic. The analytical method was optimised and validated using NIST standard reference material (SRM 1649a Urban Dust). The 16 priority PAH listed in the US-EPA were Soxhlet-extracted from filtered particulate matter and then fractionated using on-column chromatography. The aromatic fraction was quantified by gas chromatography-mass spectrometry. Real samples of particles collected in Seville (Spain) were analysed using the validated method. Values for the total concentration of PAH in the air, as well as the concentrations of each PAH in six particle-size ranges were obtained. Values of the PAH in TSP, PM₁₀, PM_2.5 and PM₁ were assessed.     

EDS X-Ray Investigation of Interdiffusion in Au–Ni Micro- and Nanolayers

The interdiffusion process in thin and thick (500nm–60µm) Au–Ni layers deposited on different substrates is studied using the EDS technique. In-depth X-ray analysis based on the Pouchou and Pichoir method is applied for obtaining the concentration profiles in nanometre scale multi-layers. A theoretical analysis using the Darken method is employed for modelling interdiffusion in the Au–Ni system. Computer simulations, where intrinsic diffusivities of the Au and Ni are functions of composition, are presented and compared with experimental results.     

Kinetics of CO oxidation on the surface of heterophase catalysts. Modeling by the Monte Carlo method

The Monte Carlo method has been used to simulate CO oxidation on a lattice consisting of various alternating patches: M1, where s(CO)>s(O₂) and M2, where s(CO)2). The reaction is shown to proceed over all the surface at low temperature as CO_ads spillover from M1 to M2 and backwards.     

游离氧化钙,氧化镁连续测定的电导法研究

研究了乙二醇对氧化钙，氧化镁的提取条件，利用乙二醇提取氧化钙后在催化剂存在下继续提取氧化镁，建立了电导法连续测定ＣａＯ，ＭｇＯ分析方法，可用于水泥熟料中游离氧化钙，氧化镁的测定。     

系数倍率法同时测定铁钴镍三组分的研究

本文运用了在乙酸缓冲液中铁，钴，镍与亚硝基红盐（ＮＲＳ）生成有色配合物光吸收的差异，分别采用系数倍率法消除相互之间的干扰取得了满意的结果。