Crystal structure of CoUO<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript> · 5H<Subscript>2</Subscript>O at 293 K

Single crystals of cobalt uranyl sulfate are grown. The crystal structure is established by X-ray diffraction: the orthorhombic system, sp. gr. Pmc2₁, a = 6.452(2) Å, b = 8.295(2) Å, c = 11.288(3) Å, R₁ = 0.0303, wR₂ = 0.0735 for reflections with I > 2σ(I). The structure of CoUO₂(SO₄)₂ · 5H₂O consists of infinite two-dimensional uncharged [CoUO₂(SO₄)₂H₂O]_2∞ layers, which are linked to each other by hydrogen bonds.     

Synthesis and crystal structure of a new representative of the Rb2U2MoO10 uranomolybdate series

A new representative of the Rb₂U₂MoO₁₀ uranomolybdate series, was synthesized; its single crystals were grown and studied by X-ray diffraction. The atomic crystal structure was solved: monoclinic system, space group P2₁/c, a = 8.542(1) Å, b = 15.360(2) Å, c = 8.436(1) Å, b = 104.279(3)°, R ₁ = 0.064 for 1817 independent reflections with F > 4σ(F). The crystal structure is built of negatively charged infinite corrugated [U₂MoO₁₀] _2∞ ^δ? layers, which are linked through rubidium cations arranged between them. The compound was studied by IR spectroscopy; the absorption bands in the spectrum were assigned.     

Electronic to vibrational energy transfer assisted by interacting transition dipole moments: a quantum model for the nonadiabatic I2(E) + CF4 collisions

We report a theoretical study of nonadiabatic transitions within the first-tier ion-pair states of molecular iodine induced by collisions with CF(4). We propose a model that treats the partner as a spherical particle with internal vibrational structure. Potential energy surfaces and nonadiabatic matrix elements for the I(2)-CF(4) system are evaluated using the diatomics-in-molecule perturbation theory. A special form of the intermolecular perturbation theory for quasi-degenerate electronic states is implemented to evaluate the corrections to the long-range interaction of transition dipole moments of colliding molecules. The collision dynamics is studied by using an approximate quantum scattering approach that takes into account the coupling of electronic and vibrational degrees of freedom. Comparison with available experimental data on the rate constants and product state distributions demonstrates a good performance of the model. The interaction of the transition dipole moments is shown to induce very efficient excitation of the dipole-allowed upsilon(3) and upsilon(4) modes of the CF(4) partner. These transitions proceed predominantly through the near-resonant E-V energy transfer. The resonant character of the partner's excitation and the large mismatch in vibrational frequencies allow one to deduce the partner's vibrational product state distributions from the distributions measured for the molecule. The perspectives of the proposed theoretical model for treating a broad range of molecular collisions involving the spherical top partners are discussed.     

Effect of a small dispersion on self-focusing in a spatially one-dimensional case

The effect of a small dispersion on the self-focusing of solutions of equations of nonlinear geometric optics in a spatially one-dimensional case has been studied. This effect in the leading order is described by a universal special solution of the nonlinear Schrödinger equation, k]which is isomonodromic. The analytical and asymptotic properties of this universal solution have been considered.     

In situ muSR and NMR investigation of methanol dissociation on carbon-supported nanoscaled Pt-Ru catalyst

In situ muSR and nuclear magnetic resonance (NMR) experiments on the investigation of methanol decomposition on Pt-Ru nanoscaled catalyst supported on Vulcan XC-72 carbon black (Pt-Ru/Vulcan XC-72) are presented. Avoided-level-crossing muon spin resonance measurements reveal the resonance line at magnetic field 2.018 T, we assign to transient CH₂?OMu? formaldehyde muonated radical. Results obtained allow us to estimate the contribution of chemical decomposition reaction process for the formaldehyde—carbon oxide—hydrogen conversion on Pt-Ru/Vulcan XC-72 catalytic material. NMR spectrum of the methanol covered Pt-Ru/Vulcan XC-72 consists of three broad resonance lines. Two of them are assigned to OH and CH₃ groups of methanol bound to the carbon black surface. Following the existing literature, which indicates that polymerization of formaldehyde readily takes place when the monomer is adsorbed on some active surface, the third one is assigned to the resonance signal of oligomeric species of formaldehyde. Taking into account the results of our experiments on electrochemical hydrogenation of carbon nanotubes, we do not exclude that the hydrogen arising as a result of methanol decomposition would also contribute to this signal. The high surface area of amorphous carbon nanoparticles of Vulcan XC-72 is favourable to adsorb the hydrogen on their surface.     

Synthesis of binuclear C-carboranylmercury and B-carboranylthallium complexes containing cyclopentadienyl and (dimethylaminomethylcyclopentadienyl)manganese tricarbonyl ligands

The interaction of (CO)₃MnC₅H₃RLi (R=2-Me₂NCH₂, H) with 2-Ph-1-HgBr-1, 2-C₂B₁₀H₁₀ and (1, 7-C₂H₂B₁₀H₉-9)TlCl₂ gives the corresponding C-carboranylmercury and B-carboranylthallium derivatives with M-C bonds, in which the C atom belongs to the cyclopentadienyl ring of the substituted cymantrenyl fragment. The structures of the compounds obtained are discussed on the basis of¹H NMR and IR spectral data.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 586–587, March, 1993.     

Jet impingement on a wall of arbitrary configuration

The problem of jet impingement on a wall of arbitrary configuration is studied. A curvilinear wall is approximated by a polygonal line with a fairly large number of links and a method based on the classical approach of Joukowski and Michell is applied to solve the problem. By successive displacement of the jet it is established that at a certain wall configuration the problem can have two solutions, one of which is multivalent. The limiting flow regimes characterized by the total disappearance of one of the jets formed after the division of the main impinging jet are revealed. An attempt to model the well-known experiment on the stable position of a small sphere lying on the horizontal bottom, when a slender water jet falls on it, is made. In the modeling the sphere is replaced by a circular cylinder in a separationless flow. It is numerically shown that any jet displacement to the right or to the left from the position corresponding to zero horizontal force acting on the cylinder leads to the generation of an oppositely directed nonzero force which indicates the absolute instability of the cylinder in the separationless jet flow.     

Effect of electrochemical treatment on structural properties of conical carbon nanotubes

Interaction of multiwalled conical carbon nanotubes (CNTs) with hydrogen during their electrochemical treatment was studied by galvanostatic measurements and Raman spectroscopy. The structural changes occurring in the conical walls of the CNTs in consequence of the hydrogenation were investigated by using X-ray diffraction (XRD). The results obtained show that hydrogen sorption by conical CNTs is reversible. XRD studies revealed that the electrochemical hydrogenation leads to a change in the diffraction peak profile (2θ=26^°) and its position corresponding to the interplanar distance in conical CNTs. The results indicate structural changes occurring in the conical walls of the CNTs during hydrogenation. We assume that these structural changes can be caused by the hydrogen intercalation into the interplanar spaces of conical CNTs. Thus, the charge/discharge and structure data can be explained by the existence in this system of physically adsorbed molecular hydrogen and chemically bound atomic hydrogen.