The Fine Structure of Alkali Metal Atoms in Inelastic Collisions with Hydrogen

Optics and Spectroscopy - A method is proposed for calculating the rate constants of inelastic processes occurring during collisions of alkali metal atoms and their positive ions with hydrogen...     

Bacteriochlorophyll Fluorescence of Green Sulfur Bacteria in Anaerobic Zone of Two Natural Water Bodies

Absorption and fluorescence spectra for living cells of green sulfur bacteria inhabiting the anaerobic zone of two meromictic lakes separated from the White Sea have been studied. The spectral-optical properties of pure cultures of green-colored and brown-colored species of green sulfur bacteria Chlorobium phaeovibrioides have been compared, and the content of bacteriochlorophyll molecules in one bacterial cell of each species has been estimated. The method of separating the contributions of different groups of green sulfuric bacteria to bacteriochlorophyll fluorescence was applied for a mixture of two species of bacteria with different pigmentation. The depth distributions of fluorescence intensity and concentration of bacteriochlorophylls for microorganisms inhabiting the Trekhtzvetnoe and Elovoe lakes at the Kandalaksha Gulf of the White Sea were plotted.     

Growth, refined structural and spectroscopic characteristics of Tm-doped NaGd(WO4)2 single crystals

The details of Tm³⁺-doped NaGd(WO₄)₂ single-crystal growth are discussed, the results of precise investigations of its structural and spectroscopic characteristics, as well as the analysis of cross-relaxation process of Tm³⁺ ions (³H₄→³F₄, ³H₆→³F₄) in this crystal are presented. Based on the Judd–Ofelt theory, three intensity parameters, spontaneous emission probabilities, fluorescence branching ratios and fluorescence quantum efficiency from ³H₄ and ³F₄ levels were refined.     

Study of crack resistance of TiAlN coatings by scratch testing

Scratch tests were performed to study failure mechanisms in TiAlN coatings deposited on substrates from steel 12Cr18Ni9Ti. It is shown that coating failure begins with crack generation at the apices of pile-ups formed along the scratch due to plastic ploughing of the substrate material. With further increase in indentation load the failure process is governed by the competition between tensile stresses behind the indenter arising due to friction force and stresses at the contact area periphery due to coating bending under normal load. Substrate pretreatment by Ti ion beams is shown to simultaneously increase the hardness and crack resistance of TiAlN coatings.     

The computation of dynamical moduli of solids under pressure

On the basis of the theory of finite strains, expressions are obtained in general form for the effective adiabatic second order elastic constants of crystals of any symmetry in terms of the isothermal elastic constants of second, third, and higher orders in the free energy decomposition. These expressions are used in the case of crystals of cubic symmetry under hydrostatic conditions to find the elastic wave velocities in mono- and polycrystals, and their pressure dependences. The polycrystal was considered as an isotropic body consisting of a large number of cubic monocrystals. The isotropic elastic constants were calculated from theoretical and experimental results for monocrystals in the Voigt-Reuss-Hill approximation. A method of applying this approximation to thermodynamic effective second order elastic constants is proposed. The results of a computation are compared with data of experiments to measure the sound velocity in polycrystalline NaCl and CsCl specimens under pressures to 100 kbar. The results of this comparison are discussed.Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 4, pp. 162–170, July–August, 1972.     

Structure and lattice dynamics of the high-pressure phase in the ScF3 crystal

The high-pressure phase of the ScF₃ crystal has been studied using synchrotron radiation diffraction and Raman scattering. This phase existing in the pressure range 0.6–3.2 GPa is optically anisotropic: its structure is described by space group R $ \bar 3 $ \bar 3 c, Z = 2, and the transition is associated with the rotation of ScF6 octahedra around the threefold axis. The pressure dependences of the lattice parameters and the rotation angle have been determined. The number of lines in the Raman spectrum corresponds to the expected number for this structure; the recovery of soft modes has been observed above the phase transition.     

Investigations of vinyl esters of the furan series

The vinyl esters of trans--(2-furyl) acrylic acid, furan-2-carboxylic acid, 5-bromofuran2-carboxylic acid, and 5-nitrofuran-2-carboxylic acid were synthesized by the reaction of the corresponding acids with acetylene and vinyl acetate. Mercuric acetate and boron trifluoride etherate were used as catalysts for the transvinylation of acids of the furan series. The structures of the vinyl esters obtained were proved by IR and PMR spectroscopy. The distribution of the -electron density in the molecules of four of the synthesized vinyl and ethyl esters was studied by means of quantum-chemical calculations by the SCF MO LCAO method (Pople variant) using the Raman and UV absorption spectra.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1443–1447, November, 1972.     

15N and17O NMR spectra of vinyl ethers of pyridine and quinoline

Conclusions ¹⁵N (¹⁴N) and¹⁷O NMR spectra have been obtained on vinyl ethers of pyridine and quinoline, with unenriched samples. The principal factor determining the chemical shifts is p- conjugation of the unshared pairs of the heteroatom with the unsaturated fragments of the molecule; an additional contribution in the case of the¹⁵N signals comes from interaction of the nitrogen atom with a proton through space.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 769–773, April, 1987.     

Synthesis of New Amphiphilic Comb-Like Copolymers Based on Maleic Anhydride and α-Olefins

Summary: Novel amphiphilic comb-like poly(α-olefin-co-maleic anhydride) with a controlled ratio of hydrophilic (polyoxyethylene) and hydrophobic (polymethylene) side chains have been synthesized and characterized. The comb-like copolymers are soluble in organic and aqueous media and form micelles whose behaviour could be correlated to the chemical structure of polymers. We foresee that amphiphilic properties of the novel comb-like polymers are obviously the basis of new architectures in solution which could be used in a broad range of applications. Using micelles from these copolymers, silver nanoparticles with a narrow particle size distribution have been obtained as stable dispersion in both polar and non-polar media.     

Peculiarities of NMR spectra of heterospin complexes

Experimental investigation and theoretical simulation of the unusual phenomenon of multiple broadening and narrowing of NMR signals due to the temperature variation of a solution of the stereochemically non-rigid heterospin Ni²⁺ complex with stable nitroxide were performed. The investigation of the temperature dependence of the NMR signals of stereochemically non-rigid heterospin systems can be used for choosing conditions for growing heterospin single crystals containing molecules in a definite conformation.