Temperature dependence of the lowest frequency <Emphasis Type="BoldItalic">E</Emphasis><Subscript><Emphasis Type="Bold">g</Emphasis></Subscript> Raman mode in laser-synthesized anatase TiO<Subscript>2</Subscript> nanopowder

Nanosized titanium dioxide (TiO₂) powder was prepared by a laser-induced pyrolysis. Specific surface area of the as-grown powder measured by BET method was 109 m²/g. The grain size (14.5 nm) estimated from these data coincides well with the crystallite size (12.3 nm) determined by XRD measurements. The average grain size (∼35 nm) obtained from the subsequent SEM measurements refers to considerable agglomeration of nanoparticles. Raman spectroscopy has been used to investigate the structural properties of TiO₂ nanopowder and its anatase structure is confirmed. The blueshift and broadening of the lowest frequency E_g Raman mode at temperature range ∼25–550 K have been analyzed using a phonon-confinement model. Dominant influence of the strong anharmonic effect at higher temperatures was demonstrated. PACS 81.07.Wx; 78.30.-j; 63.22.+m     

Glassy behavior of electrons near metal-insulator transitions

The emergence of glassy behavior of electrons is investigated for systems close to disorder-driven and interaction-driven metal-insulator transitions. Our results indicate that Anderson localization effects strongly stabilize such glassy behavior, while Mott localization tends to suppress it. We predict the emergence of an intermediate metallic glassy phase separating the insulator from the normal metal. This effect is expected to be most pronounced for sufficiently disordered systems, in agreement with recent experimental observations.     

Experimental indications for the response of the spectators to the participant blast

Precise momentum distributions of identified projectile fragments, formed in the reactions 238U+Pb and 238U+Ti at 1A GeV, are measured with a high-resolution magnetic spectrometer. With increasing mass loss, the velocities first decrease as expected from previously established systematics, then level off, and finally increase again. Light fragments are on the average even faster than the projectiles. This finding is interpreted as the response of the spectators to the participant blast. The reacceleration of projectile spectators is sensitive to the nuclear mean field and provides a new tool for investigating the equation of state of nuclear matter.     

Lattice dynamics and phase diagrams for hydrogen bonded systems

Abstract

A variational correlated ground state wave-function theory is applied to investigate the high-pressure deformation of hydrogen-bond potential described by a double Morse potential functions. The evolution of the hydrogen bond potential with increasing pressure and the effects of deuterium isotope substitution on the quantum-fluctuation-driven phenomena are discussed. The theory was employed for predicting and interpreting the pressure dependence of the phase transition temperatue for KDP-like ferroelectrics and NQR-frequency coefficients for several deuterated and undeuterated crystals.     

A semiclassical model of the interior of Uranus

Abstract

Using the mass and radius of Uranus, as determined by Voyager, and a particular semiclassical theory of dense matter, a model of its interior has been developed. Details of the model, the underlying theory and possible sources of discrepancies with recent work on this topic are briefly presented.     

Spectrophotometric Study of Catechol Oxidation by Aerial O2 in Alkaline Aqueous Solutions Containing Mg(II) Ions.

Electronic absorption spectroscopy was employed to study the aerial oxidation of catechol (1,2-benzenediol) in alkaline aqueous solution containing an excess of Mg(II) ions. Graphical analysis by the matrix method of UV spectra recorded at regular time intervals gave a good fit for two absorbing species in solution. Based on this result and our earlier ESR spectroscopic investigations we concluded that two main absorbing species in this system are Mg(II)-spin stabilized o-benzosemiquinone anion radical and C-C dimer formed by the nucleophilic attack of catecholate anion on o-benzoquinone. Although the formation of 1,2,4-benzenetriol during the catechol oxidation has been detected in some ESR studies its presence was not indicated by this analysis probably because of the low and/or stable steady state concentration throughout the experiment.     

Vibrational Structure of the B—X System of Isotopic Ago Molecules

Spectra of ¹⁰⁷Ag¹⁸O and ¹⁰⁷Ag¹⁶O molecules have been obtained in a low-pressure arc in oxygen atmosphere, and recorded with medium dispersion. Vibrational assignments for the bands of B ²π —X²π system were verified by the study of the oxygen isotope effect, and the vibrational constants were obtained for the states involved in transitions.     

Matrix Lax Polynomials, Geometry of Prym Varieties and Systems of Hess–Appel’rot Type

We consider a four-dimensional generalization of Hess–Appel’rot system and costruct its Lax pair. Both classical and algebro-geometric integration procedure are proceeded. The algebro-geometric integration is based on deep facts from geometry of Prym varieties such as the Mumford relation and Mumford-Dalalyan theory. The integration is similar to the integration of Lagrange bitop which has recetly been performed by the authors.     

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Excitation of adsorbed molecule vibrations in low energy electron scattering

We develop a theory of low energy electron loss spectroscopy of vibrational modes of molecules adsorbed on metal surfaces. Differential and total cross sections are calculated in the Distorted Wave Born Approximation, assuming i) strong elastic scattering on the metal surface, ii) direct electron-molecule interaction via the electric dipole field associated with the molecular vibration. The angular distributions are calculated and discussed for molecules adsorbed at various distances above the metal surface and for several electron energies and impact angles. The influence of electronic screening of dipolar oscillations is discussed and the consequences of the classical induced image dipoles are explored. It is shown that the metal surface selection rule known in IR spectroscopy is only approximately valid in electron scattering. Finally, we give numerical estimates of the inelastic scattering cross sections for the stretching vibrations of CO molecule adsorbed on transition metal surfaces, in reasonable agreement with experiments.