Multipulse regimes of excitation of optical superradiance due to a two-photon transition

Multimode triggered optical superradiance due to a two-photon transition is theoretically studied. Kinetic equations are derived for the dynamics of cooperative development of coherence and population inversion of optical centers interacting with each other through a common field of emitted photons. Various regimes of triggering of optical superradiance due to a two-photon transition are considered. The possibility of creating a quantum photomultiplier on the basis of the triggered optical superradiance is discussed.     

Reaction of onium salts with nucleophilic reagents

Russian Chemical Bulletin -     

Study of CO oxidation on the (111) face of nickel during Ni?NiO phase transition

CO oxidation on the (111) face of Ni has been studied over a wide temperature range and reactant ratio in CO+O₂ reaction mixtures. A significant nonstationary increase in the reaction rate due to the formation of a two-dimensional surface oxide has been found. Subsequent formation of threedimensional NiO(111) phase sharply decreases the CO oxidation rate.

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CO (111) Ni (CO+O₂). , . , NiO(111) CO.

     

Structural transformations of silicates upon prolonged grinding

Structural changes in diopside, CaMgSi₂O₆, and wollastonite, CaSiO₃, upon prolonged (up to 84 h) grinding in a mechanic agate mortar under environmental conditions were studied. X-ray phase analysis and specific surface measurements were used to show that the stage of amorphization of the starting substances under mechanical treatment is followed by the formation of a partially ordered phase whose reflexes correspond to reflexes of α-quartz. Possible mechanisms of the structural transformations were discussed.     

Stabilization of silver clusters by matrices of various chemical nature

Silver clusters having unusual optical and chemical properties and characterized by a band at 320–330 nm, are shown to be stabilized by solid matrices of various chemical nature.

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, , 320–330 , .

     

Catalysis of thiophene hydrogenolysis by bimetallic sulfide catalysts of different compositions

The activity of sulfide catalysts M_I/SiO₂, M_I/WS₂, (M_I,W)/SiO₂ and (Ni,M_II)/SiO₂ (M_I is a first row transition metal, and M_II=Nb, Mo, W or Re) in the thiophene hydrogenolysis reaction has been studied. Activities of mono- and bimetallic catalysts are found to change in the same manner depending upon the nature of M_I. The formation of a sulfide bimetallic species (SBMS) is suggested.

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M_I/SiO₂, M_I/WS₂, (M_I,W)/SiO₂ (Ni, M_II)/SiO₂, M_I — , M_II–Nb, Mo, W, Re. - M_I. .

     

Oxidation of carbon monoxide on the (001) plane of ruthenium

The Ru(001) plane is shown to possess high but variable activity in the reaction of CO oxidation. A drop of activity is attributed to the transformation of surface oxygen into the unreactive state.

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, (001) Ru , . .

     

CRYSTAL STRUCTURE AND X-RAY CRYSTALLOGRAPHIC ANALYSIS OF THE BINUCLEAR CLUSTER THIOCYANATE COMPLEX OF NIOBIUM(IV)

Journal of Structural Chemistry - The structure of a binuclear niobium(IV) thiocyanate complex (Bu4N)4[Nb2(μ2-S2)2(NCS)8]·H2O (1·H2O) is studied by X-ray crystallography. Compound...     

Electrotransport in binary iron-based metal melts

The mobility of ions in binary iron-based liquid metal systems is calculated for the first time, based on studies on the specific resistance and self-diffusion coefficient in a wide range of concentrations. It is established that iron ions move toward the anode in Fe–V and Fe–Mo systems, and toward the cathode in Fe–W and Fe–Pt systems; i.e., there is inversion of electrotransport for iron ions. When the concentration of a component is reduced, the mobility of its ions grows in modulus.     

Influence of mechanoactivation on the perovskite structure

The crystal structure of the perovskite rhombohedral modification before and after mechanoactivation in air and in carbon dioxide is studied using the X-ray diffraction method. It is shown that a medium in which an as-grown perovskite crystal is milled influences the degree of its amorphization but does not influence either the size of ordered areas or the distortion of titanium and calcium coordination polyhedra. It is found that the rate of perovskite milling is smaller than the rate of pseudowollastonite milling under the same conditions.