Interferences and Methods for Their Elimination in the Determination of Lanthanum as LaO by Laser-Enhanced Molecular Flame Ionization Spectrometry

Interfering effects of some elements on the determination of lanthanum as LaO in a natural gas–air flame by laser-enhanced molecular ionization spectrometry were studied. It was demonstrated that easily ionized elements (Li, K, Na, Mg) exert an ionization effect; in addition, sodium introduces spectral interference. Techniques were proposed for the elimination of these interfering effects.     

A Spectrophotometric and Chromatographic Study on the Products of Radiation-induced Oxidation of 3,5-Dihydroxytoluene in Aqueous Solutions

Aerated aqueous solutions of 3,5-dihydroxytoluene (₇) irradiated with single electron pulses in the dark or under exposure to a light flux were studied by pulse radiolysis and high-performance liquid chromatography. The two types of high-energy particles, -rays and fast electrons, were compared. The complex mechanism of radiation-induced redox reactions occurring in the aqueous solutions of ₇ and giving low-molecular and long-chain oxidation products was experimentally proved. Transient species of the radiation-induced oxidation of ₇ that absorb light in the spectral range of 250–420 nm and have a lifetime longer than a millisecond were observed.     

Raman spectra and structural features of ClOF2 + cation in a solution of anhydrous HF

The Raman spectra of ClOF₂ ⁺ cation in solutions of anhydrous HF were studied. In the ClOF₂ ⁺HF₂ ⁻ and ClOF₂ ⁺BF₄ ⁻−HF systems, this cation exists as a pyramidal structure (C _s symmetry), while in the ClOF₂ ⁺AuF₆ ⁻−HF system, it exists as a planar structure (C _2v symmetry). Based on nonempirical calculations by the Hartree-Fock-Roothaan method, an explanation for the dependence of the structure of the ClOF₂ ⁺ cation on the nature of the anion was proposed. For the Cl−O bond vibrations, the correlation functions of vibrational and rotational relaxations were calculated, and the characteristic times of these processes were determined. The main contribution to the formation of the band contours corresponding to the above-mentioned modes is made by the vibrational dephasing. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 432–437, March, 1998.     

Influence of Ionizing Radiation on the Properties of a Nanodispersed PdO/CeO<Subscript>2</Subscript> Catalyst in the Reaction of Low-Temperature Carbon Monoxide Oxidation

The effect of electron-beam irradiation on the catalytic properties of PdO/CeO₂ has been examined. It has been found that irradiation in the range of 15–30 kGy results in an increase in the concentration of the radical anion [O^?], thereby enhancing the catalytic activity of PdO/CeO₂.     

Formation kinetics of nanoparticles as the basis for simulating the generation mechanism of Liesegang rings in gels

An approach has been proposed for determining the space-time parameters of the formation process of Liesegang rings. This approach relates the processes of the formation of nanoparticles and dense periodic precipitates from them. Dynamic light scattering is employed to reveal periodic variations in the intensity of light scattered by nanoparticles with different sizes, from which Liesegang rings are formed. A relationship between the periods of the variations in the intensity of light scattered by nanoparticles (microscopic process) and the times of the formation of Liesegang rings as a whole (macroscopic process) has been found.     

Laser-enhanced molecular-ionization spectrometry of BaO and LuO in low-temperature flame

The molecular ionization spectra of BaO and LuO were recorded in low-temperature natural gas-air flame with excitation laser wavelengths in the range 440–480 and 535–575 nm. Addition excitation of barium and lutetium monoxides by a second laser quantum did not amplify the ionization signal. One-step laser excitation with wavelengths of 549.3 and 466.2 nm is optimal for BaO and LuO, respectively.     

Initiation of Self-Oscillations at Loss of Stability of Spatially-Periodic, Three-Dimensional Viscous Flows with Respect to Long-Wave Perturbations

We study the long-wave asymptotics of a secondary regime formed at loss of stability of a stationary spatially-periodic flow, as one of the periods grows without bound (the wavenumber vanishes). It is shown that if the main flow, aligned with the long period, is non-zero and certain nondegeneracy conditions are satisfied, then a self-oscillation regime branches off the main solution as the viscosity decreases, both soft and rigid modes of loss of stability being possible. Explicit formulas for the main terms of the asymptotics are derived. Examples of the self-oscillations on particular flows are calculated and the behavior of the fluid particle paths in the self-oscillation traveling-wave' regime branching off the shear flow is studied.