Reactive Ion Surface Scattering as an Eley–Rideal Process: A Molecular Dynamics Study into the Abstraction Reaction Mechanism by Low Energy Cs<sup>+</sup> From Pt(111)

Lahaye, R.J.W.E.; Kang, Heon

doi:10.1002/cphc.200300983

Cited by 19 publications

(49 citation statements)

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“…However, the ER scenario for ions in RIS is different to the one with neutral atoms, since the recombination mechanism is due to the electrostatic ion-adsorbate attraction (ion-dipole) and it is effective only for physisorbed atoms. 41,42 The angular dependence of the molecular translational energy is accounted for in the molecular beam experiments by Ueta et al, 24 and it is in reasonable agreement with the theoretical value from MD simulations that use the atomic effusive incident beam, as shown in Figure 1 for Θ f < 40 • inplane directions. At Θ f > 40 • N 2 molecules originated by ER contribute only to 3% of the total N 2 intensity, and therefore those E f / E i values are dominated by N 2 reflection.…”

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confidence: 72%

Efficient N₂ Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Blanco-Rey

Díaz

Bocan

et al. 2013

J. Phys. Chem. Lett.

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Using molecular dynamics simulations and potential energy surfaces of ab-initio quality, we show that direct pick-up of N adsorbates by gas-phase N is a highly efficient channel for N 2 formation on Ag(111). This recombination process, called Eley-Rideal, was traditionally associated to lighter projectiles and regarded as marginal, but here we obtain reactivities for * To whom correspondence should be addressed TOC GraphicKeywords: Gas-surface interactions, Eley-Rideal reactions, scattering, potential energy surfaces, molecular dynamics. 2Among the various elementary processes that occur in everyday gas-surface reactions, those resulting in the recombination and desorption of molecules deserve a special attention, as they regulate the replenishment of the surface active sites. One of these processes, the direct Eley-Rideal (ER) recombination has been found to be a marginal phenomenon, only observed experimentally for incoming light atoms (H,D). [1][2][3][4][5][6][7][8][9] Originally postulated as an atom exchange, 10-12 the ER process is nowadays assigned to the direct recombination of an incoming gas-phase species that picks up a surface adsorbate to conform a molecular compound that desorbs during the collision. Even if the initial measurements pointed to ER cross sections of about 2 − 5 Å 2 , 4,6,9 subsequent theoretical studies demonstrated that they were around one order of magnitude smaller because most of the recombination events proceed after few collisions of the incoming (H,D) atom with the surface, i.e., through the slower hot-atom (HA) process. [13][14][15][16][17][18] In the scope of reactive ion scattering (RIS), C abstraction from a graphite surface by N + ions has been characterised by experiments, and found to happen after several collisions with the substrate 19 Recombination of neutral atomic species heavier than (H,D) has been experimentally studied in the context of CO formation and CO oxidation on metal surfaces. In all cases, CO and CO 2 formation is dominated by the Langmuir-Hinshelwood (LH) recombination in which the species involved in the reaction are fully thermalized with the surface. [20][21][22] Also in these systems, the direct ER pick-up events are accepted to play a very minor role. Within this context, the recent experiments by Ueta et al. suggesting the existence of direct recombination on the N-covered Ag(111) surface between gas-phase and adsorbed N atoms are certainly intriguing. 23,24 All the more so when recent simulations of N 2 formation on the W(100) surface also exhibit low ER probabilities. 25 In this letter we demonstrate that thermal and hyperthermal gas-phase N scattered off Ncovered Ag(111) is indeed a prototype system that fulfills all the requirements to observe a highly efficient direct ER recombination. This outcome poses a new scenario for the study of gas-surface interactions, as it shows that fast direct recombination channels may be active in contrast to the usual assumption of neglecting them, specially for large atomic projectiles. 3The comple...

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confidence: 72%

Efficient N₂ Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Blanco-Rey

Díaz

Bocan

et al. 2013

J. Phys. Chem. Lett.

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“…2 Since then, the RIS process has been examined on various surfaces and molecular adsorbate systems, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and the RIS mechanism has been investigated theoretically by using molecular dynamics simulations. [48][49][50][51][52][53] These studies indicate that the nature of the RIS process is quite universal and, therefore, it can be applied to the analysis of molecules on surfaces.…”

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confidence: 99%

“…[4][5][6][48][49][50][51] In the early RIS experiments with chemisorbed species, where very small RIS yields (~10 -4 ) were observed, the RIS processes were considered to occur via a two-step mechanism; the Cs + impact causes collision-induced desorption (CID) of adsorbates and the Cs + -molecule association occurs in the outgoing trajectory. [4][5][6] However, in the later experiments, much higher (up to ~1) RIS yields were observed for small molecules physisorbed on surfaces, such as CO 2 , H2O, and noble gases on metal surfaces [51][52][53] and frozen water films.…”

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confidence: 99%

“…8,[12][13][14][15]32 The early two-step mechanism cannot explain the high RIS yields observed in these experiments. Studies using classical molecular dynamics simulations [48][49][50] support the idea that the RIS process actually occurs via a one-step abstraction mechanism, which is categorized as an Eley-Rideal (ER) type surface reaction. Figure 4 illustrates this one-step abstraction mechanism with four representative snapshots of the simulated RIS trajectory.…”

mentioning

confidence: 99%

“…In this case, optimal RIS conditions for surface analysis can be found for a specular scattering geometry at the angle between 90 o -120 o (45 o -60 o for both incident beam and detector angles with respect to the surface normal), according to the results of angle-resolved RIS studies 6,16 and MD simulations. 50 RIS experiments can be performed in several different modes of operation depending on the information desired. First, for the purpose of surface analysis and molecular identification, a mass spectrum of RIS signals is obtained from a sample by scanning a QMS in an appropriate mass range.…”

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Reactive Ion Scattering of Low Energy Cs⁺from Surfaces. A Technique for Surface Molecular Analysis

Kang¹

2011

Bulletin of the Korean Chemical Society

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Although the currently available surface spectroscopic techniques provide powerful means of studying atoms and simple molecules on surfaces, the identification of complex molecules and functional groups is a major concern in surface analysis. This article describes a recently developed method of surface molecular analysis based on reactive ion scattering (RIS) of low energy (< 100 eV) Cs + beams. The RIS method can detect surface molecules via a mechanism in which a Cs + projectile picks up an adsorbate from the surface during the scattering process. The basic principles of the method are reviewed and its applications are discussed by showing several examples from studies of molecules and their reactions on surfaces.

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Direct Observation of Segregation of Sodium and Chloride Ions at an Ice Surface

et al. 2005

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Distribution of electrolyte ions near the surface of water or ice is a subject of interest in both fundamental chemistry and atmospheric chemistry of sea-salt aerosols and ice particles. The ion distribution at the surface of these particles may affect their reaction with ozone and organic species in the troposphere and the generation of reactive halogen species. [1,2] In early studies, the surface of aqueous solutions containing simple electrolytes such as alkali halides was thought to be deficient of ions, as inferred from the surface tension of solutions.[3] Molecular dynamics (MD) simulations have been widely employed since the 1990s to study the molecular details of solvation and segregation of atomic ions in water clusters.[4-8] MD calculations [6][7][8] predict that the large and polarizable anions are more readily available at the surface than the small nonpolarizable cations, in both water slab models [8] and clusters of finite sizes. [6,7,9] Photoelectron spectroscopic studies [10] of anionic water clusters in the gas phase support the surface residence of the larger halide anions by comparing the ionization energies with calculations. Further studies of the anionic clusters [X À (H 2 O) 1-5 , X= F, Cl, Br and I] using vibrational spectroscopy [11][12][13] indicate that the larger halides (Cl À , Br À and I À ) are solvated at the surface of water clusters. The spectra from clusters with the larger halides reveal a hydrogen-bonding network of water molecules, which supports surface solvation of anions, whereas the spectra from the F À -containing clusters lack such hydrogen-bonding features. [12b, 13] A limited number of experimental studies were performed to investigate the ion distribution at the surface of real aqueous solutions, and basically none at ice surfaces. Morgner and co-workers [14] measured He(I) photoelectron spectra from the surface of concentrated aqueous solutions of CsF and observed that the salt concentration is strongly depleted in the surface region. MD simulations from the same group [15] explain the phenomena by the circumstance that the ions near the surface mostly keep their first solvation shell intact. Using Xray photoelectron spectroscopy and scanning electron microscopy, Ghosal et al. [16] observed selective segregation of Br À ions to the surface of a NaCl crystal, which was slightly doped with Br À ions, under conditions of relative humidity, where the condensed water films caused partial dissolution of the crystal surface. Their results provide the first experimental evidence for preferential segregation of large halide anions to the surface of mixed alkali halides. More recently, vibrational sum frequency generation spectroscopy for sodium halide solutions [17] [a] J

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Reactive Ion Surface Scattering as an Eley–Rideal Process: A Molecular Dynamics Study into the Abstraction Reaction Mechanism by Low Energy Cs⁺ From Pt(111)

Cited by 19 publications

References 65 publications

Efficient N₂ Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Efficient N₂ Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Reactive Ion Scattering of Low Energy Cs⁺from Surfaces. A Technique for Surface Molecular Analysis

Direct Observation of Segregation of Sodium and Chloride Ions at an Ice Surface

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Reactive Ion Surface Scattering as an Eley–Rideal Process: A Molecular Dynamics Study into the Abstraction Reaction Mechanism by Low Energy Cs+ From Pt(111)

Cited by 19 publications

References 65 publications

Efficient N2 Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Efficient N2 Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Reactive Ion Scattering of Low Energy Cs+from Surfaces. A Technique for Surface Molecular Analysis

Direct Observation of Segregation of Sodium and Chloride Ions at an Ice Surface

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Product

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Reactive Ion Surface Scattering as an Eley–Rideal Process: A Molecular Dynamics Study into the Abstraction Reaction Mechanism by Low Energy Cs⁺ From Pt(111)

Efficient N₂ Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Efficient N₂ Formation on Ag(111) by Eley–Rideal Recombination of Hyperthermal Atoms

Reactive Ion Scattering of Low Energy Cs⁺from Surfaces. A Technique for Surface Molecular Analysis