NMR and spin-lattice relaxation rate of89Y,63Cu in radiation disordered YBa2Cu3O6.9

NMR line shifts and spin-lattice relaxation rates of⁸⁹Y and⁶³Cu in YBa₂Cu₃O_6.9 were measured in disordered samples irradiated by fast neutrons with a fluence of: ?=5·10¹⁸ cm^?2 (T _c ^ons =70 K), ?=1.2·10¹⁹ cm^?2 (T _c ^ons =20 K), in order to investigate the evolution of spin susceptibility χ_S under irradiation. According to the data obtained, χ_S decreases markedly as structural disorder accumulates in the samples. The variation of χ_S is related closely to that observed in oxygen-depleted YBa₂Cu₃O_7?δ compounds with nearly the sameT _c value. The data for yttrium display some features that are absent in oxygen-depleted samples. The different temperature dependence of the⁸⁹Y and⁶³Cu Knight shifts and the increase of the⁸⁹Y spin-lattice relaxation rate in irradiated samples are discussed in terms of the electron localization effects arising in the CuO₂ planes due to the radiation-induced structural disorder.     

Effective Charge in LiNbO3 Films Fabricated by Radio-Frequency Magnetron Sputtering Method

Physics of the Solid State - Amorphous Li–Nb–O films were deposited onto Si substrates by radio-frequency magnetron sputtering method. The fabricated heterostructures demonstrated the...     

The electrophilic addition of thiols to olefins: A theoretical and experimental study

Density functional theory with the B3LYP hybrid functional and 6–31G* basis set was used to study the geometric and electronic structure of H₂C = CHR (R = H, CH₃, C₂H₅, C₃H₇, C₄H₉, and C₅H₁₁) olefins, their carbocations formed in the addition of the proton to the olefins, R′-S-H aliphatic thiols (R′ = H, CH₃, C₂H₅, and C₃H₇), the products of the addition of thiols to carbocations, and the final products of the addition of thiols to olefins. The proton affinity of the olefins and the products of the addition of thiols to olefins was calculated. The conclusion was drawn that the limiting stage in the nonradical addition of thiols to olefins catalyzed by acids was proton transfer from the protonated reaction product to the olefin. The theoretical results were compared with the experimental data on the electrophilic addition of polymercaptan to heptene-1.     

Synthesis of nanosized titanium dioxide from tetrabutoxytitanium

Mesoporous TiO₂ has been obtained by template synthesis. The introduction of a surfactant in the hydrolysis of tetrabutoxytitanium in aqueous ethanol allows the structure of the resulting material to be controlled. The amorphous TiO₂ resulting from hydrolysis turns into anatase on being calcined at 300°C. As determined by X-ray diffraction, the anatase crystallite size is 70 nm in the presence of the highest surfactant concentration examined and 210 nm in the absence of a surfactant. Amorphous materials have been characterized by electron microscopy and differential thermal analysis. The ultimate benzene adsorption value has been determined for calcined mesoporous TiO₂.     

Particle-in-cell plus direct simulation Monte Carlo (PIC-DSMC)approach for self-consistent plasma-gas simulations

The particle-in-cell (PIC) and direct simulation Monte Carlo (DSMC) approaches have been combined into a PIC-DSMC model for self-consistent simulations of low-temperature collisional plasmas and the background gas. This novel approach is based on the weighting collision simulation scheme allowing for disparate number densities and time scales of different species. The applicability of the developed algorithm is illustrated by simulations of one-dimensional direct current and two-dimensional magnetron sputtering discharges in argon. An appreciable effect of the energetic discharge species on the density, temperature, and flow field of the background gas shows the importance of the coupled plasma-gas simulation for such technologies as sputtering, dry etching, plasma enhanced vapor deposition, etc     

The initiation of the addition of thiyl radicals at the C≡C bond by AlBr3 complexes with disulfides

The geometric and electronic structures of R-S-S-R disulfides (R =-C₂H₅,-C₆H₄-CH₃, and-CH₂-C₆H₅), their complexes with one and two AlBr₃ (A) molecules, and the products of the dissociation of the S-S bond with the formation of radical complexes R-SA^. and thiyl radicals R-S^. were studied by the density functional theory method with the B3LYP hybrid functional. The enthalpies and Gibbs energies of S-S bond dissociation in disulfides and complexes were calculated. Complexes of A with ditolyl-and dibenzyldisulfides easily dissociated at the S-S bond, whereas diethyldisulfide formed stable complexes with A and did not dissociate. Experimentally, stilbene derivatives were obtained and studied by physicochemical methods. These compounds were prepared in the reaction of initial ditolyl-and dibenzyldisulfides with diphenylacetylene in the presence of AlBr₃. Diethyldisulfides did not experience such transformations. The theoretical and experimental results are compared.     

About the limits of existence of α-cluster structure in nuclei

The shape of the d-α coincidence spectrum from the reaction ¹²C(⁶Li, d)¹⁶O(α)¹²C in the region corresponding to the 20.9 MeV 7^? level in ¹⁶O has been measured. Also, measurements of the α-particle elastic scattering excitation functions on ¹²C and ¹⁶O have been made in the regions corresponding to the α-cluster levels found in the (⁶Li, d) reactions. A comparison of the d-α coincidence spectra and excitation functions allows us to draw conclusions about splitting of the α-cluster states and region of their existence.     

Short-range order in Fe<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>(<Emphasis Type="Italic">x</Emphasis>=0.05−0.08) alloys with induced magnetic anisotropy

Previously, iron—silicon alloys were investigated using X-ray diffraction and Mössbauer spectroscopy. It was demonstrated that, at low silicon concentrations, the alloys undergo a local separation into regions of the α iron phase depleted in silicon and silicon-rich clusters with a B2 ordering. The structure of locally ordered regions of the B2 phase is characterized by a pair ordering of silicon atoms: the Si—Si pairs are formed by next-nearest neighbors, and the axes of pairs are oriented along the 〈100〉 directions, which are the easy-magnetization axes. The thermomagnetic treatment in a constant magnetic field applied along the 〈100〉 axis induces an axial magnetic anisotropy, results in the formation of an anisotropic distribution of the B2 phase, and leads to a slight decrease in the volume fraction of the coordination 6: 2 with two silicon atoms in the first coordination shell of the iron atom. Therefore, the formation of an anisotropic local order of pairs of silicon atoms occurs as a result of their reorientation.     

Role of Energy Transfer in Conversion of Light to Electric Energy

The role of nonradiative inductive-resonance energy transfer between molecules of Coumarine-7 and rhodamine dyes in the conversion of light into electric energy is studied. It is ascertained that the co-sensitization of a TiO₂ solar cell by donor and acceptor molecules leads to an increase of the efficiency of conversion of light to energy. The measurements show that it is due to a widening of the photosensitivity of a cell into the blue region of the spectrum. The increase of the total energy absorbed promotes increasing the number of generated charge carriers at the interface of TiO₂ and dyes.