State-resolved gas-surface reactivity measurements revealed that vibrational excitation of nu3 (the antisymmetric C-H stretch) activates methane dissociation more efficiently than does translational energy. Methane molecules in the ground state require 45 kilojoules per mole (kJ/mol) energy to attain same enhancement provided by 36 kJ/mol excitation. This result contradicts a key assumption underlying statistical theories and provides direct experimental evidence central role can play...

Energy redistribution, including the many phonon-assisted and electronically assisted energy-exchange processes at a gas-metal interface, can hamper vibrationally mediated selectivity in chemical reactions. We establish that these limitations do not prevent bond-selective control of heterogeneously catalyzed reaction. State-resolved gas-surface scattering measurements show nu1 C-H stretch vibration trideuteromethane (CHD3) selectively activates bond cleavage on Ni(111) surface....

Although important to heterogeneous catalysis, the ability accurately model reactions of polyatomic molecules with metal surfaces has not kept pace developments in gas phase dynamics. Partnering specific reaction parameter (SRP) approach density functional theory ab initio molecular dynamics (AIMD) extends our metals quantitative accuracy from only lightest reactant, H2, essentially all molecules. This is demonstrated AIMD calculations on CHD3 + Ni(111) which SRP fitted supersonic beam...

State-resolved measurements on clean Ni(100) and Ni(111) surfaces quantify the reactivity of ${\mathrm{CH}}_{4}$ excited to $v=3$ ${\ensuremath{\nu}}_{4}$ bend vibration. A comparison with prior data reveals that $3{\ensuremath{\nu}}_{4}$ is significantly less effective than ${\ensuremath{\nu}}_{3}$ $\mathrm{C}\mathrm{\text{\ensuremath{-}}}\mathrm{H}$ stretch at promoting dissociative chemisorption, even though contains 30% more energy. These results contradict statistical theories...

The interaction of platinum with water plays a key role in (electro)catalysis. Herein, we describe combined theoretical and experimental study that resolves the preferred adsorption structure wetting Pt(111)-step type adjacent (111) terraces. Double stranded lines wet step edge forming tetragons dissimilar hydrogen bonds within between lines. Our results qualitatively explain observations desorption impact our thinking solvation at Pt electrochemical interface.

Vibrational state resolved measurements of methane's dissociation on Ni(111) show a strong surface temperature dependence near the translational energy threshold for reaction. The reactivity molecules excited to v = 1 ν3 C−H stretching vibration and incident with 40 kJ mol−1 increased 8-fold as from 90 475 K. This enhancement is much larger than that reported earlier studies at higher energies. These results support recent calculations predict an important role lattice deformation in...

A long-standing challenge in the study of heterogeneously catalyzed reactions on silver surfaces has been determination what oxygen species are greatest chemical importance. This is due to coexistence several different surface reconstructions oxidized surfaces. further complication subsurface (Osub). Osub O atoms absorbed into near region a metal, and expected alter terms chemistry structure; however, these effects have yet be well characterized. We studied Ag(111) after exposure gas-phase...

The sticking coefficient for D2O impinging on crystalline ice was determined incident translational energies between 0.3 and 0.7 eV H2O at eV. These experiments were done using directed molecular beams, allowing precise control of the angle energy. Experiments also performed to measure intensity energy scattered molecules as a function scattering angle. results show that near unity, slightly increasing with decreasing However, even lowest energy, some did not stick from surface. We observe...

The experimental observations of vibrational mode- and bond-selective chemistry at the gas-surface interface indicate that energy redistribution within reaction complex is not statistical on timescale reaction. Such behavior a key prerequisite for efforts to use selective excitation control technologically important interface. This paper outlines framework understanding origin non-statistical reactivity surfaces. model focuses kinetic competition between intramolecular (IVR) complex, which...

Oxygen chemisorption on rhodium surfaces gives rise to several surface structures depending the total oxygen coverage. In this study, Rh(111) was exposed O2 or O + O2, and formed at coverages greater than equal 0.5 ML were imaged using scanning tunneling microscopy (STM). The STM images showed that (2 × 1)-O adlayer domains are predominant surface. Exposure of atoms yielded ML; (1 observed form along terrace step edges, their areal density increased with exposure. However, adlayers still...

We report on a combined TPD and STM study of O2 adsorption dissociation various Pt surfaces with varying (111) terrace widths either (110) or (100) step geometries. Our quantitative results show that stepped adsorb considerably more oxygen at 100 K, regardless width, than planar Pt(111). These suggest dissociates the well lower required for temperature-induced planes. The amount desorbing from recombinative desorption adsorbed atoms is also greater surfaces. In addition, partitioning between...

We herein report on the chemical and physical changes that occur in thin films of poly(methyl methacrylate), PMMA, induced by exposure to high-energy vacuum ultraviolet radiation a supersonic beam neutral, ground electronic state O(3P) atomic oxygen. A combination situ quartz crystal microbalance Fourier-transform infrared reflection−absorption spectroscopy were used determine photochemical reaction kinetics mechanisms during irradiation. The surface morphological measured with force...

The surface dynamics of amorphous and semicrystalline polymer films have been measured using helium atom scattering. Time-of-flight data were collected to resolve the elastic inelastic scattering components in diffuse neutral atoms from a thin poly(ethylene terephthalate) film. Debye–Waller attenuation was observed for both phases by recording decay elastically scattered with increasing temperature. Thermal measurements specular geometry yielded perpendicular mean-square displacements 2.7•10...

An electrochemical method using pulsed alternating current etching (PACE) to produce atomically sharp scanning tunneling microscopy (STM) tips is presented. Arduino Uno microcontroller was used control the number and duration of (AC) pulses, allowing for ready optimization procedures both Pt:Ir W a single apparatus. prepared constant AC power were compared. Tips fashioned PACE sharper than those etched with continuous alone. an initial coarse stage followed by fine PACE. The potential...

The uptake and chemical speciation of oxygen in on Ag(111) surface is described. An was exposed to gas-phase atoms under ultrahigh vacuum compatible conditions at various temperatures. O quantified using temperature-programmed desorption measurements showed that exposures temperatures above 500 K yielded only surface-adsorbed a single reconstruction. At below K, continued past saturation, maximum the with respect exposure temperature observed 450 K. A model where must diffuse out subsurface...

The translational and angular intensity dependence of CO2 produced from the reaction CO with an initial oxygen coverage 0.5 ML ≤ ΘO 1.6 on Rh(111) at a surface temperature 450 K was measured. This range coverages goes only absorbed O to both adsorbed selvedge O. measured energy is independent larger than steady-state experiments [Colonell et al. J. Chem. Phys. 1995, 103, 6677], which were done lower coverages, but follows trend that higher leads faster CO2. well-described by sharply peaked...

In heterogeneously catalyzed oxidation reactions on metal surfaces, advantageous oxygenaceous species proffer lower barrier reaction pathways. order to utilize such better, it is essential understand what are present, how they formed, and under conditions available for reaction. Oxides, adsorbed oxygen, subsurface oxygen each form Rh(111) surfaces thus provide the opportunity distinguish contributions of overall reactivity. an effort elucidate relevant sites catalytically active rhodium a...

Subsurface oxygen is known to form in transition metals, and thought be an important aspect of their ability catalyze chemical reactions. The formation subsurface not, however, equivalent across all catalytically relevant metals. As a result, it difficult predict the stability ease as well how absorbed affects physical properties metal. In comparing stepped platinum surface, Pt(5 5 3), responds exposure gas-phase atoms under ultra-high vacuum conditions planar Rh(1 1 1), we are able...

Abstract The epoxidation of olefins on Ag/O systems is a significant industrial‐scale process within heterogeneous catalysis. However, the details surface reaction remain controversial, and it has been highly challenging to reconcile findings from cataltyic studies under conditions with detailed static carefully controlled ultra‐high vacuum (UHV) conditions. In this study, we combine molecular beam scattering ion imaging techniques explore partial oxidation styrene. This experimental...

The flow of energy from the impact site a heavy, translationally energetic xenon atom on an ice surface leads to several non-equilibrium events. central focus this paper is collision-induced desorption (sputtering) water molecules into gas-phase surface. Sputtering strongly activated with respect translational energy, and threshold for was observed. To best understand these results, we discuss our findings in context other sputtering studies molecular solids. yield quite small; differential...