Kinetic studies of antimony and selenium atomization processes including a chemical modifier during their determination by electrothermal atomic absorption spectrometry

We have studied antimony and selenium atomization processes including a chemical matrix modifier (palladium-containing activated carbon) during their determination by electrothermal atomic absorption spectrometry. We have developed and fine-tuned an experimental setup for determining the kinetic characteristics (activation energy and frequency factor) for element atomization processes from measurements in the initial section of the analytical signal. We provide a rationale for the most likely mechanism for the interactions that occur. The results of the kinetic studies of the atomization processes showed that the modifier we developed was highly effective, as a result of formation of a thermally stable condensed system C-Pd-A (where A is the analyte). __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 530–534, July–August, 2006.     

Influence of iron-subgroup metals on the atomization of silicon in a graphite furnace

The regime of atomization of Si in the presence of Fe-subgroup metals was investigated with the use of a “Saturn” spectrophotometer and a “Graphit-2” electrothermic atomizer. The optimal operating parameters of the atomizer have been determined. It was established that the optimal value of the ashing and the atomization temperatures are, respectively, 900–1000°C and 2400°C, the optimal rate of temperature rise at the stage of atomization is 1400 K/sec, and the appropriate amount of Fe, Co and Ni additions is 1–2 μg. It was established that the formation of gaseous silicides of the Fe-subgroup metals, the dissociation energies of which are lower than the dissociation energies of Si oxides and carbides, increases the sensitivity for determination of Si. To whom correspondences should be addressed. Institute of Single Crystals, National Academy of Sciences of Ukraine, 60, Lenin Ave., Khar'kov, 310001, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 153–157, March–April, 1999.     

Effect on silicon atomization of tungsten-assisted modification of atomic-absorption spectrometer graphite furnaces

The influence of a tungsten-assisted modification to a tubular graphite furnace in an atomic absorption spectrometer on the Si atomization signal characteristics is studied. A hypothesis is proposed that explains a shift of Si atomization peaks for the modified furnaces compared with the standard ones. Some advantages of the standard tubular graphite furnaces modified by tungsten and the prospects for their application are demonstrated. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 1, pp. 13–17, January–February, 2008.     

电热原子吸收光谱法中原子化过程动力学研究的最新进展

本文评述了1994－2000年年间电热原子吸收光谱法中原子化过程动力学研究的最新进展,内容包括升温原子化过程动力学参数测定方法、等温原子化过程动力学参数测定方法、动力学参数测定方法的比较、双先导物升温原子化过程的动力学模型、考虑原子蒸气再沉积过程的升温原子化过程的动力学模型以及原子化器表面、基体改进剂及干扰物对分析物原子化过程的影响。引用文献31篇。     

Cosmology with non-minimally coupled k-field

We consider a non-minimally coupled (with gravity) scalar field with non-canonical kinetic energy. The form of the kinetic term is of Dirac–Born–Infeld form. We study the early evolution of the universe when it is sourced only by the k-field, as well as late time evolution when both the matter and k-field are present. For the k-field, we have considered constant potential as well as potential inspired from boundary string field theory. We show that it is possible to have an inflationary solution in early time as well as late time accelerating phases. The solutions also exhibit attractor properties in a sense that they do not depend on the initial conditions for certain values of the parameters.     

Isotherms of real gases

A refined kinetic equation is proposed for the adsorption of molecules on a solid surface, taking account of factors such as the interaction of the molecules and their migration over the surface. Detailed theoretical analysis of the process is complemented by experimental verification of the resulting formulas by pulsed photodesorption. The time of monolayer formation is found to be two orders of magnitude greater than the values calculated from the Langmuir isotherm. This indicates that the new formula for the adsorption isotherm satisfactorily describes the process in high vacuum. Kazan’ State Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 41–48, April, 1998.     

Hydrogen in amorphous and crystalline ytterbium films

Ytterbium vapor condensation on a liquid-helium cooled substrate in a hydrogen atmosphere is used to obtain Yb-H films containing up to 55 at.% hydrogen. Various thermodynamic and kinetic parameters of the transition of these films from the amorphous to the crystalline state (a→c transition) are investigated along with the electrical conductivity of these states. It is shown that the investigated properties of Yb-H films containing up to 40 at.% hydrogen are essentially indistinguishable from those of pure Yb films in the temperature interval 4.2–293 K. Increasing the hydrogen concentration to 55 at.% leads to an insignificant increase in the electrical resistivity, the kinetic temperature, and the activation energy of the a→c transition, and also to a decrease of the propagation speed of self-maintaining avalanche (explosive) crystallization. Reasons for the observed influence of hydrogen on the properties of Yb-H films are analyzed. The examined low-temperature Yb-H condensates can be characterized as a “frozen” solid solution of hydrogen in ytterbium in the temperature interval 4.2–293 K. Storing such films at room temperature leads to the formation of ionic ytterbium dihydride YbH₂. Fiz. Tverd. Tela (St. Petersburg) 41, 177–182 (February 1999)     

“Gelios” compact atomic-absorption spectrometer with flame-free atomizer

The principle of operation and specifications of the “GELIOS” atomic-absorption spectrometer with a flame-free (tungsten) atomizer are described. Operation of the device under conditions of pulsed atomization and automatic control of the coil temperature is discussed. A distinctive feature of the device is use of a personal computer to control the coil temperature. Information on the software, test maintenance, reliability, and repairability of the spectrometer is provided. Belarusian State University, 4, F. Skorina Ave., Minsk, 220050, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 4, pp. 604–607, July–August, 1998.     

On the vierbein formalism of general relativity

Both the Einstein–Hilbert action and the Einstein equations are discussed under the absolute vierbein formalism. Taking advantage of this form, we prove that the “kinetic energy” term, i.e., the quadratic term of time derivative term, in the Lagrangian of the Einstein–Hilbert action is non-positive definitive. And then, we present two groups of coordinate conditions that lead to positive definitive kinetic energy term in the Lagrangian, as well as the corresponding actions with positive definitive kinetic energy term, respectively. Based on the ADM decomposition, the Hamiltonian representation and canonical quantization of general relativity taking advantage of the actions with positive definitive kinetic energy term are discussed; especially, the Hamiltonian constraints with positive definitive kinetic energy term are given, respectively. Finally, we present a group of gauge conditions such that there is not any second time derivative term in the ten Einstein equations.     

Facile synthesis of additive-assisted nano goethite powder and its application for fluoride remediation

The present article describes a novel synthesis route for nano-sized goethite (α-FeOOH) using hydrazine sulphate as an additive. The X-ray diffraction (XRD) peaks of synthesized powder matched well with those of α-FeOOH. Transmission electron microscopy (TEM) showed the particles of irregular shape in the range of 1–10 nm. Batch adsorption experiments for fluoride uptake were performed to study the influence of various experimental parameters such as contact time (10 min to 7 h), initial fluoride concentration (10–150 mg L⁻¹), pH (2–11.6) and the presence of competing anions. The time data fitted well to pseudo-second-order kinetic model. The fluoride removal passed through broad maxima in pH ranges of 6–8. High adsorption capacity of 59 mg g⁻¹ goethite was obtained. The isothermic data fitted well to Freundlich model. The presence of other ions namely chloride and sulphate adversely affected fluoride removal. Fluoride from contaminated water sample could be successfully brought down from 10.25 to 0.5 mg L⁻¹.     

Navier–Stokes Transport Coefficients of <Emphasis Type="Italic">d</Emphasis>-Dimensional Granular Binary Mixtures at Low Density

The Navier–Stokes transport coefficients for binary mixtures of smooth inelastic hard disks or spheres under gravity are determined from the Boltzmann kinetic theory by application of the Chapman–Enskog method for states near the local homogeneous cooling state. It is shown that the Navier–Stokes transport coefficients are not affected by the presence of gravity. As in the elastic case, the transport coefficients of the mixture verify a set of coupled linear integral equations that are approximately solved by using the leading terms in a Sonine polynomial expansion. The results reported here extend previous calculations (Garzó, V., Dufty, J.W. in Phys. Fluids 14:1476–1490, 2002) to an arbitrary number of dimensions and provide explicit expressions for the seven Navier–Stokes transport coefficients in terms of the coefficients of restitution and the masses, composition, and sizes of the constituents of the mixture. In addition, to check the accuracy of our theory, the inelastic Boltzmann equation is also numerically solved by means of the direct simulation Monte Carlo method to evaluate the diffusion and shear viscosity coefficients for hard disks. The comparison shows a good agreement over a wide range of values of the coefficients of restitution and the parameters of the mixture (masses and sizes).     

Domain walls in a generalized Chern–Simons model

In this paper we study the structure of one dimensional topological solitons in a generalized Abelian-Higgs Chern–Simons model where the kinetic term is non-canonical. We present an example of an analytical self-dual electrically charged soliton solution which has a finite momentum per unit length along its direction. We compared the physical properties of our soliton with those for wall of Jackiw–Lee–Weinberg wall presented in Jackiw et al. (Phys. Rev. D 42:3488, 1990) to conclude that the non-canonical kinetic term can make the wall “thicker” redistributing uniformly the momentum flow along it.     

Band structure and dominating electron-scattering mechanisms in Hg<Subscript>1−<Emphasis Type="Italic">x</Emphasis>−<Emphasis Type="Italic">y</Emphasis></Subscript>Mn<Subscript>x</Subscript>Fe<Subscript>y</Subscript>Se

Magnetic and kinetic properties as well as transmission and absorption spectra of Hg _1−x−y Mn _x Fe _ySe (0.09 ≤ x ≤ 0.099 and 0.001 ≤ y ≤ 0.01) crystals are investigated at H ≈ 0.5–6 kOe in the temperature range T = 77–300 K. The band parameters are determined on the basis of experimental data. It is found that in the crystals under study at T ≈ 300 K, electron scattering by polar optical phonons dominates, direct optical band-to-band transitions occur, and replacement of a part of Mn atoms by Fe for x + y = 0.1 results in an increase in E_g ^op with Fe content. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 35–39, March, 2007.     

Photoinduced self-limited low-temperature growth of ultra-thin silicon-oxide films with water vapor

The growth of ultra-thin (<2 nm) silicon-oxide films was investigated on Si(100):H, Si(111):H, and a-Si:H surfaces in a pure water atmosphere (0.1–10 Pa) at low temperatures of 30–250 °C. Oxidation was induced photochemically by pulsed F₂-laser radiation at 157 nm. The thickness and composition of the growing oxide films were monitored in real time by spectroscopic ellipsometry in the photon energy range of 1.15–4.75 eV. The mechanism of laser-induced silicon oxidation in a H₂O atmosphere is shown to differ fundamentally from the classical Deal–Grove mechanism of thermal oxidation at 900–1200 °C, as well as from the photoinduced low-temperature oxidation in an O₂ atmosphere. In particular, the film thickness essentially does not depend on temperature below 250 °C. A kinetic model is developed for low-temperature silicon oxidation in a H₂O atmosphere. According to this model, the growth is limited at small thicknesses by the oxidation reaction and at larger thicknesses by reactions of the diffusing oxidizing species in the oxide layer. Very good agreement is established between this kinetic model and the ellipsometric measurements and the temperature and pressure dependence of the water oxidation process. PACS 82.65.+r; 07.60.Fs; 81.65.Mq; 82.50.Hp     

Strangeness enhancement

Highly effective conversion of kinetic energy into abundant particle multiplicity is the remarkable feature discovered in high energy heavy ion collisions. This short and pedagogic review addresses topical issues related to the understanding of this phenomenon, originating in the creation of the deconfined quark–gluon plasma phase. I consider in depth the apparently simple, yet sometimes misunderstood, intricate issues: a) statistical hadro-chemistry, chemical parameters, b) strange flavor chemical equilibration in quark–gluon plasma, and c) particle yields and sudden hadronization, in the historic perspective of work and competition with my friend József Zimányi.     

Pulsed cathodoluminescence of feldspars

We have studied the spectral and kinetic characteristics of pulsed cathodoluminescence of feldspars (albite, microcline, amazonite) in the time range 10⁻⁸–10⁻² sec and the temperature range 28–300 K. We have shown that the bands in the UV region of the spectrum (5.39, 4.35, and 3.75 eV) are due to intrinsic luminescence of the crystals. The ratio of the intensities of these bands characterizes the phase composition of the mineral: in the luminescence spectra of microcline, for all temperatures the 4.35 eV band dominates; in the pulsed cathodoluminescence spectra of albite, the bands at 3.75 eV (at 300 K) and 5.39 eV (at 28 K) dominate. The parameters of the luminescence decay kinetics for the impurity ions Fe³⁺ and Mn²⁺ are more sensitive to local perturbations of the lattice structure than the position of the emission band maximum, and can be an effective indicator of the origin of the mineral. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 3, pp. 339–343, May–June, 2006.     

Model for the axial growth of filamentary silicon crystals

We propose a model for the axial growth of filamentary silicon crystals, based on the assumption that the crystallization occurs in a diffusion-limited regime. A kinetic equation is obtained which enables us to analyze changes in the crystal growth rate under the influence of various technological parameters. State Technical University, Voroneg. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 37–41, May, 1996.     

Excitation of metal spectra in combined glow discharge

Consideration is given to the special features of the excitation of spectra of metals (Ag, Au, Fe, Hg, Pt, and Sb) that manifest themselves in investigating spectral sources with combined glow discharge (glow discharge and capillary discharge). It is established that the proposed method for introducing a substance into a plasma makes it possible to realize two fundamentally different regimes: without evaporation and with complete evaporation and matrix atomization. It is shown that a spectral source of combined glow discharge with a nonequilibrium plasma has significant advantages for the most important analytical characteristics over quasi-equilibrium combined discharge at atmospheric pressure. The gold and platinum sensitivity in combined glow discharge is 10⁻⁷%, and the reproducibility of spectral determinations is 0.001–0.100, depending on the measurement range. A fractional separation of elements that makes it possible to analyze the phase composition of substances, particularly metals, with high sensitivity is revealed in glow discharge. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 143–147, March–April, 1997.     

Formation of excited states of atoms and ions in laser plasma from CuInS2

Emission spectra and the energy distribution of the excited-state population density of atoms and ions in erosion laser plasma from CuInS₂ with various crystal-structure orderings are analyzed. It is shown that increased ordering of the target crystal structure causes the excited-state energies of indium atoms generated in the laser erosion plume to increase and that sulfur atoms always emit only in transitions from highly excited states. The ratio of relative ion concentrations in the laser plasma plume is Cu⁺/In⁺/S⁺ = 0.3/0.08/2, which corresponds neither to the atomic ratio of Cu/In/S (1/1/2) in the target nor to the ratio of ionization energies. The results are explained by recombination processes for ions and by the atomization specifics of the CuInS₂ target exposed to long-wavelength radiation. The atomization consists essentially of dissociative processes expressed by CuInS₂ → CuInS + S and CuInS₂ → Cu + InS + S. The electron temperature of polycrystal (single-crystal) plasma at a distance of 1 mm from the target is 0.3 eV (0.4 eV) for atoms and 1.3 eV (2.7 eV) for ions and varies negligibly for plasma up to a distance of 7 mm from the target. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 217–223, March–April, 2008.     

Influence of the evaporation coefficient on the strong condensation of a monatomic gas

The influence of the evaporation coefficient on the supersonic condensation of a monatomic gas on a flat surface is studied on the basis of the kinetic theory. The formulation of the problem allows for the possible existence of a shock-wave type solution near the surface. The regions of admissible values of the parameters characterizing the state of the gas beyond the Knudsen layer are determined for different values of the evaporation coefficient. Zh. Tekh. Fiz. 67, 21–25 (October 1997)