A. I. Dement’ev

Laser stimulation of low-temperature dissociative recombination of electrons and oxygen molecular ions

AbstractA theory of dissociative recombination of slow electrons and molecular ions in a strong monochromatic light field is developed. The theory takes into account interference between various reaction channels and is constructed in a rigid basis adiabatic with respect to rotation (the approximation of a fixed molecular axis). The mathematical apparatus of the theory is based on the stationary formalism of the matrix of radiation collisions, whose poles correspond to “quasi-energy” states of a composite system. Along with transitions into dissociative configurations, field-induced nonadiabatic transitions into bound intermediate states of valence (non-Rydberg) configurations are considered. As a particular application of the theory, the e− + O2+(2Πg) →

Synthesis and Thermodynamic Characteristics of Aluminum, Gallium, and Indium Pivalates

O(^{2s_1 + 1} l_1 ) + O(^{2s_2 + 1} l_2 )

Theoretical study of ammonia nucleophilic addition to nitriles in platinum complexes

reaction is analyzed. A study of this reaction requires detailed information about the potential curves of the states participating in it with taking into account the external electromagnetic field (l and s are the electronic angular momenta and reaction product spins). For this purpose, the general problem is divided into three stages. At the first stage, the theoretical approach is formulated, and at the second stage, the corresponding potential curves are calculated and the main reaction mechanisms are determined. The third stage should include calculations of the total and differential cross sections. This work is concerned with the first two stages; that is, the adiabatic potential curves of the singlet and triplet dissociative states of the O2** oxygen molecule are calculated, a classification of all possible transition types is given, and reaction mechanisms in the presence of monochromatic laser radiation are determined. The frequency regions of external radiation in which these mechanisms are most effective are found.

The structure of polypropylene-TiO2 organoinorganic nanocomposites prepared via solvent crazing

Optical characteristics of the composites based on an amorphous polymer and a luminescent dye [poly(vinyl chloride)-Rhodamine 6G] prepared via solvent crazing are studied. After annealing at temperatures above glass transition temperature T g, the samples show a dramatic increase in the intensity of absorption and luminescence bands of Rhodamine Y and a marked decrease in light scattering. The observed changes are due to the diffusion of dye molecules in the polymer matrix and healing of the porous structure of crazes. The above processes are independent and proceed simultaneously. As a result, transparent composites with a low level of light scattering and with a uniform distribution of dye molecules in the polymer matrix are formed. When the PVC-Rhodamine 6G samples are annealed at temperatures above T g, dramatic changes in their spectral luminescent characteristics and color allow the above composites to be considered specific photochromic materials.

Structure and properties of hybrid PP/TiO2 nanocomposites and mesoporous TiO2 prepared via solvent crazing

Aluminum, gallium and indium pivalates, which are the most promising precursors for fabrication of oxide films in chemical vapor deposition, were synthesized. Their main thermodynamic characteristics were determined and discussed.

Ab Initio Calculations of Hydroxoplatinum Compounds: II. Binuclear Platinum(IV) Superoxo Complexes

The migration of dye molecules and healing of structural heterogeneities (internal interfaces) in an amorphous-polymer-dye system during thermal treatment are studied for the PVC-Rhodamine 6G composite prepared via the method of solvent crazing. The kinetic data on the above processes are collected through spectroscopic measurements in the visible spectral region and parallel measurements of the linear dimensions of the samples. During thermal treatment at temperatures above T g, dye molecules in the monomer modification migrate from the surface of the fibrillar craze material into the volume of the bulk polymer matrix; as a result, uniformly colored transparent samples form. In the general case, healing of the polymerdye composites includes two stages: a fast stage and a slow stage (∼1 and ∼2000 min at 85°C, respectively). The molecular mechanism of the first stage is related to the growth of the conformational entropy during shrinkage of the sample; as a result of this process, porosity decreases. The slow stage involves the disappearance of interfibrillar boundaries and occurs owing to the reptational mobility of macromolecules. The phenomenon of healing (in the broad meaning of this term) should be treated as a process that decreases the free surface energy of the polymer system.

Theoretical study of 1,3-dipolar cycloaddition of nitrones to doubly activated nitriles

The mechanism of the reaction of the ammonia nucleophilic addition to nitriles RC≡N, both free and activated in the platinum complex trans-[PtCl2(N≡CCH3)2], was studied in detail by theoretical quantumchemical methods. The reaction resulting in the formation of free or coordinated amidines proceeds through consecutive formation of an orientation complex, a six-membered cyclic transition state, and a final reaction product, in which an amidine is in the E-configuration. Water containing in a solvent plays a role of a promoter of this process. The activation effect is interpreted from the viewpoint of both kinetic and thermodynamic factors. It was shown that the mechanism of the reaction product E-Z-isomerization includes the deprotonation of the amino-group nitrogen atom, the change of the coordinated ligand conformation, and the protonation of the nitrogen atom.

The structure and properties of polymer-metallic coating interphase

A method is developed for crazing-based production of mechanically strong hybrid polypropylene film composites containing amorphous titanium dioxide nanophase (up to ∼30 wt %). As a whole, the morphology of the composite represents an interpenetrating network in which the inorganic component (TiO2) is distributed in the nanoporous structure of a polypropylene matrix. The structure and composition of amorphous titanium dioxide present an ensemble of TiO2 nanoparticles with a size of ∼1 nm (20 wt %) included in a loose network of titanium oxopolymers (80 wt %) containing ∼30 wt % side OC3H7 and OH groups bonded to titanium atoms.