Desorption of products in 193 nm photo-induced reactions in (O2+ CO) adlayers on Pt(112)

Han, Song; Matsushima, Toshiyasu

doi:10.1039/b412865f

Cited by 6 publications

(6 citation statements)

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“…It should be noted that its collimation is in the local normal of (111) or (001) terraces. This supports the idea that the collimation angle shift from the site normal in thermal CO oxidation is due to the surface smoothing effect by conduction electrons [19]. The shift is caused by insufficient translational energy of product CO 2 and suppressed by high velocity product.…”

Section: Hot-atom-assisted Reactive Co 2 Desorptionsupporting

confidence: 76%

“…Instead, the molecules that receive momentum from the hot atom leave the surface. Such hot-atom-mediated desorption was examined in photoinduced emission of O 2 and CO 2 on stepped platinum surfaces as well as of O 2 on Ag(110) and noble gases on Pt(111) in the presence of O 2 (a) [14][15][16][17][18][19][20]. On platinum surfaces, oxygen ad-molecules lie parallel to the surface plane and are likely to be localized on the terrace edge at small coverage because of the high adsorption energy.…”

Section: Hot-atom-mediated Desorptionmentioning

confidence: 99%

“…Thus, studies of such hot-atom-mediated desorption were not extended as ESDIAD work and were limited to only a few flat metal surfaces in which the hot atom does not desorb and, instead, the second species receiving the atom or its energy can leave the surface [13][14][15][16]. After detailed analysis of product desorption in ultra-violet photon-stimulated reactions of aligned O 2 on stepped Pt surfaces [17][18][19][20], it became clear that this hot-atom-mediated desorption exemplifies the typical relationship of the desorption mechanism toward the resultant spatial distributions of desorbing species, i.e., the structural information preserved in the distribution when the product is directly emitted from an associative process is different from that when a nascent fragment is first emitted parallel to the surface plane in a dissociative process [21]. In the former associative process, the collimation angle largely moves toward the local normal of the product formation site with increasing translational temperature [19].…”

mentioning

confidence: 99%

“…After detailed analysis of product desorption in ultra-violet photon-stimulated reactions of aligned O 2 on stepped Pt surfaces [17][18][19][20], it became clear that this hot-atom-mediated desorption exemplifies the typical relationship of the desorption mechanism toward the resultant spatial distributions of desorbing species, i.e., the structural information preserved in the distribution when the product is directly emitted from an associative process is different from that when a nascent fragment is first emitted parallel to the surface plane in a dissociative process [21]. In the former associative process, the collimation angle largely moves toward the local normal of the product formation site with increasing translational temperature [19]. This provides supplemental evidence for the collimation angle shift from the site normal observed in thermal CO oxidation [21].…”

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confidence: 99%

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Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

Matsushima

2009

Surface Science

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Recent progress and future developments in angle-resolved measurements of desorbing surface reaction products are reviewed for the analysis of surface species. Spatial and energy distributions of desorbing products with hyperthermal energy deliver the most direct structural information of the transition state including active intermediates and product formation sites.Knowledge of the desorption mechanism is requisite to achieve structural information since the method is directly linked to the chemical process. Structural analyses are exemplified in photoinduced O 2 desorption and CO oxidation, and compared with those from thermal N 2 O decomposition and CO oxidation as well as their applications to steady-state catalytic processes.

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Section: Hot-atom-assisted Reactive Co 2 Desorptionsupporting

confidence: 76%

Section: Hot-atom-mediated Desorptionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

Matsushima

2009

Surface Science

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“…More exactly, the collimation angles of desorbing CO 2 on stepped surfaces somewhat deviate toward the surface normal from the local normal of inclined terraces [98]. This deviation completely disappears for the CO 2 product with high translational energy, which is induced on CO-and O 2 -covered stepped surfaces by ultra-violet light [116,117]. The corrugation of the repulsive potential toward the thermal reaction product CO 2 is less than that of their geometrical shape because of the smaller translational energy.…”

Section: Normally Directed Desorption and Site Switchingmentioning

confidence: 99%

Surface reaction dynamics and energy partitioning

Matsushima

Shobatake

2010

Journal of Molecular Catalysis A: Chemical

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New approaches to surface reactions are reviewed in comparison with reaction dynamics in the gas phase. These are commonly based on product analysis before energy dissipation, in contrast to the chemical kinetics of surface reactions. Information of energy partitioning during reaction events is requisite to approach to reaction sites. In reactant adsorption, electronic excitations are exemplified to take place, showing non-adiabatic processes. On the other hand, in product desorption, spatial and energy distributions of desorbing products with hyperthermal energy can deliver the most direct structural information of the transition state including active intermediates and product formation sites. Typical analyses are shown in both N 2 O decomposition and CO oxidation on noble metals.Keywords; Surface reaction dynamics, Energy partitioning, Angular distribution, N 2 O decomposition, NO reduction, CO oxidation, Palladium, Rhodium, Platinum Chemical kinetics and reaction dynamicsThe mechanisms of chemical reactions on solid surfaces have been mostly examined from the viewpoint of chemical kinetics. The resultant mechanism is frequently short-lived because surface chemical kinetics describes the reaction rate in a phenomenological way as a function of the reactant coverage and surface temperature, proposing a consistent reaction mechanism.Most of the mechanisms deduced on ill-defined surfaces along these lines were discarded in the 1960s after re-examination by surface science techniques including vibration and photoelectron spectroscopies on well-defined surfaces [1,2]. This passive status of surface chemical kinetics has not changed even after the examination of many simulations for the description of the inhomogeneous reactivity of surface species from a mean-field approximation [3] or Monte Carlo simulations on lattice gas models [4]. Fortunately, surface 3 science has explained the mechanism of the remarkable sensitivity of chemical reactions toward surface structures, for example, in the synthesis of ammonia (N 2 +3H 2 →2NH 3 ) on iron surfaces [5] and CO oxidation (CO+O 2 →CO 2 ) on platinum metals [6]. Our understanding is, however, still far from that of gas-phase reactions. We still do not have a suitable method for directly obtaining structural information about the reaction site or active intermediates through the reaction itself. In gas-phase reactions, methods for approaching the potential energy surface (PES) have been established using both chemical kinetics and reaction dynamics [7]. This paper reviews energy partitioning requisite for surface reaction dynamics in both reactant adsorption and product desorption. In the former, electronic excitations take place, showing non-adiabatic processes. In the latter, knowledge of this partitioning opens reaction dynamics focusing on spatial and energy distributions of desorbing products, which can deliver structural information of active intermediates and product formation sites.In general, a chemical reaction must be characterized with respect to not...

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Dynamics of Surface Reactions

Ertl

2008

Handbook of Heterogeneous Catalysis

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Catalysis concerns the rate of a chemical reaction which is usually expressed as a function of the concentrations of the species involved in the reaction and a set of rate constants k i which depend on temperature T. Within the framework of transition state theory (TST) [1], which forms the basis of chemical kinetics, the latter are given bywhereby E* is the activation energy (= the height of the energy barrier along the 'reaction coordinate', i.e. the path with minimum energy with respect to all other degrees of freedom for nuclear motion). The term ΔS *The basic idea of TST consists in the assumption that at all stages along the reaction coordinate thermal equilibrium is established, so that the temperature (T) is the only essential (macroscopic) parameter. This requires that energy exchange between the various degrees of freedom of the particle interacting with the surface and the heat bath of the solid occur much faster than the process of chemical transformation. This chapter will discuss effects, for which this condition is not fulfilled and hence the observed phenomena are governed by dynamics rather than by kinetics. Energy exchange between adsorbate and solidAn estimate of the typical energy relaxation time of a chemisorbed particle, t relax , can be obtained from ob-

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Desorption of products in 193 nm photo-induced reactions in (O2+ CO) adlayers on Pt(112)

Cited by 6 publications

References 44 publications

Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

Surface species studied by angle-resolved product desorption: Emission mechanism and spatial distribution

Surface reaction dynamics and energy partitioning

Dynamics of Surface Reactions

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