Existence of a “Hot” Atom Mechanism for the Dissociation of O₂ on Pt(111)

The dissociation of O2 on a Pt(111) surface was studied by variable temperature scanning tunneling microscopy at 150–106 K. The two oxygen atoms created by the dissociation appear in pairs, with average distances of two lattice constants. Since thermal random walk sets in only at around 200 K, with a diffusion barrier of 0.43 eV and a preexponential factor of 10−6.3cm2s−1, the distribution of distances at around 160 K evidences nonthermal processes during the dissociation. It is concluded that transient ballistic motion exists, where the short range traveled is in agreement with recent molecular dynamics studies

Social Networking Sites, Personalization, and Trust in Government: Empirical Evidence for a Mediation Model

Political communication via social media might well counter the eroding political trust. In particular, social networking sites (SNS) enable direct flows of communication between citizens and the political elite, thereby reducing social and political gaps. Based on the concept of personalization of politics, we argue that interactions with politicians on SNS affect trust in government through a two-step process: First, interactions on SNS make citizens evaluate politicians’ characters more favorably. Second, these evaluations serve as cues for the citizens to develop or withdraw trust in government. We test indirect effects using four character traits as mediators: leadership, benevolence, responsiveness, and likeability. A representative online survey (n = 1117; in Germany) reveals that interactions with politicians on SNS increase the perceived likeability of candidates, and thus also trust in government. However, they do not affect the evaluation of the other traits: leadership, benevolence, and responsiveness

Formation mechanism of the O-induced added-row reconstruction on Ag(110): A low-temperature STM study

The formation of the O-induced added-row reconstruction on Ag(110) was studied by scanning tunneling microscopy at 190 K. At this temperature critical surface processes are slow enough to be followed on the atomic scale. Ag atoms, which are required for the formation of the reconstruction, detach from steps in a row-wise fashion, starting from kink sites. The growth rate of the added rows is constant and controlled by the detachment rate of Ag atoms from the steps. The data provide evidence for a reconstruction mechanism in which the release of the metal atoms from the steps and the formation of lateral oxygen metal bonds are independent processes

Das Remstal, das Land am mittleren Neckar und die Schwäbische Alb

DAS REMSTAL, DAS LAND AM MITTLEREN NECKAR UND DIE SCHWÄBISCHE ALB Württembergische ländliche Rechtsquellen (-) Das Remstal, das Land am mittleren Neckar und die Schwäbische Alb (2) ([3]) Einband (-) Titelseite ([3]) Vorwort ([5]) Einleitung ([7]) Inhaltsverzeichnis ([9]) Kloster Adelberg ([1]) Altwürttembergische Ämter Schorndorf, Waiblingen, Winnenden (28) Altwürttembergische Ämter Stuttgart und Cannstatt (82) Kloster Denkendorf (136) Reichsstadt Eßlingen (144) Ritterschaftliche Orte (171) Altwürttembergische Ämter Göppingen, Kirchheim, Nürtingen und Neuffen (364) Reichsstadt Reutlingen (388) Altwürttembergische Ämter Urach und Münsingen (410) Kloster Blaubeuren (421) Kleinere Herrschaften auf der Schwäbischen Alb (470) Herrschaft Wiesensteig (638) Kloster Zwiefalten (666) Kleinere Herrschaften im Donaugebiet (711) Register I (930) Register II (937) Druckfehler und Berichtigungen (-) Farbinformation (-) Einband (-

Die östlichen schwäbischen Landesteile

DIE ÖSTLICHEN SCHWÄBISCHEN LANDESTEILE Württembergische ländliche Rechtsquellen (-) Die östlichen schwäbischen Landesteile (1) ([1]) Einband (-) Titelseite ([1]) Vorwort ([3]) Einleitung ([5]) Inhaltsverzeichnis ([14]) Fürstentum Öttingen ([1]) Kloster Kirchheim am Ries ([148]) Deutschorden'scher Besitz ([169]) Reichsstadt Nördlingen ([177]) Fürstlich Turn und Taxis'sche Herrschaften ([196]) Altwürttembergisches Oberamt Heidenheim ([271]) Gefürstete Propstei Ellwangen ([295]) Gräflich Adelmann von Adelmannsfelden'sche Orte ([435]) Reichsstadt Aalen ([483]) Freiherr von Wöllwarth'sche Orte ([487]) Reichsstadt Gmündische Orte ([560]) Gräflich von Rechberg'sche Herrschaften ([666]) Register ([864]) Nachtrag und Berichtigungen ([887]) Farbinformation (-) Einband (-

Adsorbate-adsorbate interactions from statistical analysis of STM images: N/Ru(0001)

Atomic nitrogen on Ru(0001) was prepared by dissociative chemisorption of N2 and studied by scanning tunneling microscopy (STM) at 300 K. Nitrogen occupies the hcp threefold hollow site and is imaged as a depression with a diameter of about 5 Å. Interactions between the adsorbed nitrogen atoms were obtained by statistical analysis of STM images, by extraction of the two-dimensional pair distribution function from the arrangement of the N atoms. Since the nearest-neighbor separations could be identified with atomic precision, the pair distribution function g and hence the potential of mean force Veff were obtained as a function of the discrete neighbor sites j up to the tenth nearest neighbor. A comparison with Monte Carlo calculations for balls with a hard-sphere potential provides information about the pair potential Vpair(j): The nearest-neighbor site is strongly repulsive, the second-neighbor site is weakly repulsive, and the third-neighbor site is weakly attractive. These findings rationalize the absence of island formation and of a well-ordered 2×2 phase for the N/Ru(0001) system: At temperatures ≥300 K the attractive interaction on the third-neighbor site is too weak, while at lower temperatures the diffusion barrier of 0.9 eV represents a kinetic obstacle. The fact that the range of the interaction is identical to the diameter of the N-atom features in the STM topographs is taken as evidence that the interaction is caused by substrate-mediated electronic forces

Diffusion and Atomic Hopping of N Atoms on Ru(0001) Studied by Scanning Tunneling Microscopy

The dynamic behavior of N atoms adsorbed on a Ru(0001) surface was studied by scanning tunneling microscopy. N atoms formed by dissociation of NO molecules show an initial sharp concentration profile at atomic steps. Its decay was followed as a function of time, providing a quasicontinuum diffusion constant; the activation energy is 0.94 eV and the prefactor is 2×10−2cm2s−1. The diffusion constant was determined also at equilibrium, from statistical jumps of individual N atoms in a uniform overlayer, and is found to be identical to the Fickian value

Enhanced reactivity of adsorbed oxygen on Pd(111) induced by compression of the oxygen layer

The reaction between O atoms and CO molecules on Pd(111) was investigated by scanning tunneling microscopy (STM). CO was dosed on the (2x2)O-covered surface at temperatures between 100 and 190 K, and the structure changes were monitored by STM. CO adsorption causes compression of the (2x2)O overlayer into islands of the (2x1)O structure, followed by reaction of the O atoms to give CO2. The (2x2)O overlayer does not react with CO at temperatures up to 180 K, whereas the (2x1)O phase reacts at temperatures as low as 136 K. The analysis of the reaction kinetics reveals an activation energy for the O+CO reaction of 0.4 eV and a reaction order of 1 with respect to the O coverage

Dual-Path Mechanism for Catalytic Oxidation of Hydrogen on Platinum Surfaces

The catalytic formation of water from adsorbed hydrogen and oxygen atoms on Pt(111) was studied with scanning tunneling microscopy and high resolution electron energy loss spectroscopy. The known complexity of this reaction is explained by the strongly temperature dependent lifetime of the product H2O molecules on the surface. Below the desorption temperature water reacts with unreacted O adatoms to OHad, leading to an autocatalytic process; at higher temperatures sequential addition of H adatoms to Oad with normal kinetics takes place