Raman Spectroscopic Study of Aluminum Silicate Complextion in Acidic Solutions from 25 to 150°C

Raman spectroscopic measurements were performed on aqueous acid to neutral silica-bearing solutions (0.005 ≤ m _Si ≤ 0.02, 0 ≤ pH ≤ 8) and Al–silica solutions at temperature from 20 to 150°C. At 20°C, the spectrum of silica-bearing solutions exhibits only the bands of water and a completely polarized band at 785 cm^?1. This band is attributed to the ν₁ band of the tetrahedral Si(OH)₄ molecule. In ${\text{Si(OH)}}_{\text{4}} {\kern 1pt} {\kern 1pt} - {\kern 1pt} {\text{AlCl}}_3 {\kern 1pt} - {\kern 1pt} {\text{HCl}}$ solutions, the intensity of this band decreases with increasing Al concentration, temperature, and pH. This decrease can be explained by the formation of an inner sphere complex between Al³⁺ and Si(OH)₄ according to the reaction: ${\text{Al}}^{{\text{3 + }}} {\text{ + H}}_{\text{4}} {\text{SiO}}_{\text{4}}^{\text{0}} ({\text{aq}}){\text{ }} \Leftrightarrow {\text{ AlH}}_{\text{3}} {\text{SiO}}_{\text{4}}^{{\text{2 + }}} {\text{ + H}}^{\text{ + }} $ The fraction of complexed silica deduced from raman spectroscopic measurements is in good agreement with that calculated for the similar solution compositions and temperatures using the complexation constant generated by Pokrovski et al. ⁽²³⁾ from potentiometric measurements. At ambient temperature, the formation of aluminum silicate complex is weak and does not account for more than ca. 5 % of the total Al in most natural waters. As temperature increases, this complex becomes more significant and can dominate Al speciation in acid (pH ≤ 2) hydrothermal solutions.     

Observation of ω → π0μ+μ− decay

The results of studying the mass spectrum of μ⁺μ^?γγ systems produced in π^?p collisions at 25 and 33 GeV/c presented. The wide-aperture magnetic spectrometer with a hodoscope γ-detector was used to identify muon pairs and photons. There is a clear peak in the mass spectrum which corresponds to the decay ω → π⁰μ⁺μ^? previously not observed. The branching ratio for the decay is estimated to be 9 × 10^?5 with a systematic error of 50%.     

Inclusive production of muon pairs and vector mesons in π−N collisions at momenta 27 and 40 GeV/c

Experimental results on the investigation of inclusive production of muon pairs and vector mesons (J/ψ, ?⁰(ω)) in π^?N collisions at 27 and 40 GeV/c momenta are presented.     

Quasi-Relativism,the Narrow-Gap Property,and Forced Electron Dynamics in Solids

Narrow-gap semiconductors, used in quantum network engineering, are characterized by small effective electron masses on the Fermi level and hence by high electron mobility in the lattice. We construct an explicitly solvable model that clarifies one possible mechanism for small effective masses to appear. Another mathematical model constructed here describes a possible mechanism for using a traveling wave to control an alternating quantum current in a one-dimensional lattice.     

On the tremendous effect of an electric field on the crystal lattice of quasi-one-dimensional conductors with a charge density wave

The deformation of the lattice of quasi-one-dimensional conductors with a charge density wave deformed by an electric field has been considered. In the case of the “strong” interaction between the charge density wave and lattice, the effect of the field can be compared to the usual piezoelectric effect with a tremendous piezoelectric modulus that is larger than the value in ionic crystals by a factor of L _c/λ (λ is the period of the charge density wave and L _c is the coherence length reaching several millimeters upon the sliding of the charge density wave). The interaction between the charge density wave and lattice is likely attributed to the possibility of the interband redistribution of charges (rearrangement of covalent bonds) in the process of the deformation of certain compounds with the charge density wave. The observed and expected effects provide a way of the creation of fundamentally new actuators including those of nanometer sizes.     

Solubility and Raman Spectroscopic Study of As(III) Speciation in Organic Compound-Water Solutions. A Hydration Approach for Aqueous Arsenic in Complex Solutions

Solubilities of arsenolite (As₂O₃, cub.) were measured from 22 to 90°C in water–acetone, water–acetic acid, and water—formic acid solutions of compositions ranging from the pure organic compound to pure water. Raman spectra were obtained at ambient temperature on As-containing water–acetic acid and water–acetone solutions. Results show that arsenic solvation by these organic compounds is negligible and hydroxide species dominate As speciation over a wide range of water activity (a_{H 2 O}> 0.01). The solubility data were analyzed using an approach based on stoichiometric hydration reactions. Results show that As₂O₃ solubility can be described as a function of water activity, independently of the nature of the organic compound, by involving two neutral As hydroxide complexes: As(OH)₃ and As(OH)₃·4H₂O. Stability constants derived for these species indicate that hydration weakens with increasing temperature. Calculations using these constants show that at low temperatures the tetrahydrate As(OH)₃·4H₂O is dominant in water-rich solutions; by contrast, in high-temperature crustal fluids, As(OH)₃ becomes the major As species. The proposed hydration model can be used to analyze solubility of arsenic-bearing minerals and arsenic transport in complex H₂O–CO₂—electrolyte solutions encountered in natural and industrial environments.     

Structural and electronic evolution of the As(OH)3 molecule in high temperature aqueous solutions: an x-ray absorption investigation

The geometrical and electronic structure of the arsenious acid molecule As(OH)(3) in aqueous solutions has been investigated by x-ray absorption spectroscopy (XAS) within extended x-ray absorption spectroscopy (EXAFS) and x-ray absorption near edge structure (XANES), using realistic first-principle calculations in the latter case. This investigation was performed on aqueous solutions of arsenious acid from ambient to supercritical conditions (P = 250 and 600 bars, T 相似文献   

Two-band conduction in TiO2

The contribution of electrons and holes to the electrical conduction of titanium dioxide TiO₂ in the Si/TiO₂/Al structure is determined in experiments on the injection of minority carriers from n-type and p-type silicon layers. It is established that both electrons and holes contribute to electrical conduction of the titanium dioxide layer in the Si/TiO₂/Al structure; i.e., the electrical conduction of titanium dioxide has a two-band nature.     

Microstructure of the current channel of an atmospheric-pressure diffuse discharge in a rod-plane air gap

The multichannel structure of the current channel of an atmospheric-pressure diffuse discharge excited in a 10-cm rod-plane air gap was investigated using the imprint technique. A voltage pulse with an amplitude of 240 kV, a duration of 180 ns, and a rise time of 14 ns was applied to a 1-cm-diameter bullet-shaped cathode with a tip curvature radius of 0.2 mm; the discharge current reached 350 A. It is found that the diameter of the discharge channel in the anode plane varies in the range 2.5–9.7 mm from shot to shot. The overall imprint of the current channel is formed of 170–9500 imprints of microchannels with an average diameter of 5–20 μm. The parameters of the observed microstructure do not correlate with variations in the main electric characteristics of the discharge and the parameters of the generated X-ray pulse. It is shown that the formation of the microstructure is related to the onset of cathode-directed plasma structures developing from the anode. It is suggested that the same mechanism is responsible for both the formation of the current channels structure and the anode microstructure of diffuse nanosecond discharges developing in atmospheric-pressure air gaps with a highly nonuniform electric field.     

Spectral Asymptotics of the Harmonic Oscillator Perturbed by Bounded Potentials

Consider the operator in where q is a real function with q′ and bounded. The spectrum of T is purely discrete and consists of simple eigenvalues. We determine their asymptotics and we extend these results for complex q.Communicated by Bernard Helffersubmitted 23/04/04, accepted 26/10/04