A reversible reaction forming (---Cu---O---) strings and (Cu)6-clusters on Ag(110) shown by STM

An artificial new surface of (---Cu---O---) chains grown on Ag(110) surface was prepared by reacting a surface with Cu atoms, where the (---Cu---O---) chains grow in the [1 0] direction and are self-assembled on the Ag(110) surface in a (2 x 2)-p2mg structure. When the Cu---O/Ag(110) surface was heated in vacuum, the (---Cu---O---) chain decomposed to uniform cluster dots arranged along the [1 0] direction, where the cluster dots were composed of six Cu atoms. When the Ag(110) surface with the Cu---cluster dots was exposed to O₂, the (---Cu---O---) lines were redrawn along the [1 0] direction by reacting a s in the [1 0] direction with O₂. This is a reversible chemical reaction in one dimensional regime proved in atomic resolution.     

Magnetic and other normal properties of Y-Ba-Cu-O caused by Cu-O chain fragments

We discuss the questions related to modifications of the orthorhombic phase of YBCO. A general approach of statistical mechanics allows to determine numerically such quantities as the paramagnetic Curie constant, concentration of holes doped into Cu(2) planes from chain fragments, the fractions of copper ions in differently coordinated positions. Where the experimental information is available, we discuss a correspondence between our theoretical results end experimental ones.     

Nanostructure formation by reactions of H2O with pre-adsorbed O on a Ag(1 1 0) surface

We present results of an STM investigation of water interaction with an oxygen covered Ag(1 1 0) in the case of the O(4 × 1) reconstructed surface. Regarding the formation of one-layer-thick silver nanostructures previously demonstrated, they point to the key role of the surface temperature at which the water dosing is made. Indeed we measure silver nanostructuring for dosing temperatures lower than 235 K. We follow, in real time during the water dosing, the modifications induced at the surface for two temperatures of 200 K and 240 K. Drastic differences are exhibited. At 200 K, after an initial stage of formation of molecular assembly strips along the [0 0 1], the reactive process leading to the conversion to an OH layer occurs clearly going along with the appearance and development of quasi-rectangular silver nanostructures. At 240 K, no such initial phase is evidenced. The complete conversion to an OH row structure of the scanned area occurs with no concomitant silver nanostructure formation. The dynamical behaviour of the reaction front allows the unravelling of the key role of the developing OH row ends intersecting the remaining Ag-O rows as particular reactive adsorption sites for the completion of the OH layer.     

The steering of molecules in simple dissociation reactions

The effectiveness of steering in simple dissociation reactions has been studied by performing classical and quantum simulations on a wide range of model potentials. By parametrically varying the PES landscape, it is shown how trends in the translational energy dependence of the dissociation probability may be related to particular topographical features. The relationship between the strength of attractive and repulsive regions determines the force which a molecule feels, but in addition we show that the range of the force helps determine the degree of repositioning and reorientation. The presence of wells along the reaction coordinate is considered, and it is shown how the snarled trajectories which frequently result relate to precursor-like behaviour even in the absence of dissipative processes.     

Analysis of the kinetics of N2O-CO reaction on Pd(1 1 0)

Experimental studies indicate that the N₂O-CO reaction occurring on Pd(1 1 0) under UHV conditions exhibits a first-order kinetic phase transition in the steady-state case and also transient kinetics strongly dependent on the initial state of the system. We construct a mean-field kinetic model describing these phenomena. With a minimal number of the fitting parameters, the model reasonably reproduces the special features of the reaction kinetics.     

氢键对水杨酸酸度影响的量子化学研究

分子内氢键的形成影响羧酸的酸性,实验测定表明,水杨酸的酸性大约比苯甲酸强18倍,而其异构体——对羟基苯甲酸的酸性仅为苯甲酸的一半,已有文献从氢键形成角度定性讨论这一问题,我们采用CNDO/2法对其影响实质给予进一步的探讨,从微观角度阐述了该过程的可能机理,得到了与实验一致的结果。     

The Stable Isotopes of Oxygen in Research and Technical Applications

The stable isotopes of oxygen have proved to be efficient research tools; however, only a small fraction of the possible applications of these isotopes have been examined so far. The present progress report deals with five basic types of isotopic effects whose investigation and evaluation offer information of a new kind about physical, chemical, and biological systems and processes.     

The Electrolytic Dissociation of Mellitic Acid

An analysis of the peculiarities of the dissociation of mellitic (benzenehexacarboxylic) acid was carried out with the aid of a method previously described by the authors. Values of the degrees of dissociation for the different steps, and the concentrations of various ionized and non-ionized forms of this acid, were determined. Empirical equations are suggested for the easy approximate calculation of the degrees of dissociation of dilute solutions of mellitic acid.