Vibrationally enhanced associative photodesorption of molecular hydrogen from Ru(0001)

Vazhappilly, Tijo; Beyvers, Stephanie; Klamroth, Tillmann; Luppi, Marcello; Saalfrank, Peter

doi:10.1016/j.chemphys.2007.04.022

Cited by 20 publications

(67 citation statements)

References 60 publications

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“…Depopulation of vibrational eigenstates of adsorbates on metal substrates via formation of electron-hole pairs is expected to proceed on the picosecond time scale [7,8], or even faster [9,10]. This is about the time scale that can be reached with the 3 He spin-echo technique.…”

Section: Primary Results From These Experiments Is the Intermediate Scmentioning

confidence: 99%

Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations

Firmino

Marquardt

Gatti

et al. 2014

J. Phys. Chem. Lett.

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Diffusion rates are calculated on the basis of van Hove's formula for the dynamical structure factor (DSF) related to particle scattering at mobile adsorbates. The formula is evaluated quantum mechanically using eigenfunctions obtained from three dimensional realistic models for H/Pd(111) derived from first principle calculations. Results are compatible with experimental data for H/Ru(0001) and H/Pt(111), if one assumes that the total rate obtained from the DSF is the sum of a diffusion and a friction rate. A simple kinetic model to support this assumption is presented.

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Section: Primary Results From These Experiments Is the Intermediate Scmentioning

confidence: 99%

Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations

Firmino

Marquardt

Gatti

et al. 2014

J. Phys. Chem. Lett.

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“…Simulations modelling motion in more than two degrees of freedom of the molecule typically employ friction coefficients computed using the local density friction approximation (LDFA). 160,162 For this reason, typically only a few molecular (two) degrees of freedom are modeled in the dynamics calculations. Instead, it is assumed that each H-atom independent of the other H-atom experiences a friction force, with the friction coefficient only depending on the density of the unperturbed metal.…”

Section: D Classical Trajectory Methodsmentioning

confidence: 99%

“…156 With this method, the electronic structure of the molecule is neglected in the calculation of the friction coefficient. 160,162 2E.3 Inclusion of phonons and ehp excitation in the model: AIMDEF. Tensorial friction coefficients can be obtained with a method that does take molecular structure into account, 13 but with this method friction coefficients are expensive to calculate, restricting the use of such friction coefficients to low dimensional simulations.…”

Section: D Classical Trajectory Methodsmentioning

confidence: 99%

Quantum and classical dynamics of reactive scattering of H₂ from metal surfaces

2016

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We review the state-of-the art in dynamics calculations on the reactive scattering of H2 from metal surfaces, which is an important model system of an elementary reaction that is relevant to heterogeneous catalysis. In many applications, quantum dynamics and classical trajectory calculations are performed within the Born-Oppenheimer static surface model. However, ab initio molecular dynamics (AIMD) is finding increased use in applications aimed at modeling the effect of surface phonons on the dynamics. Molecular dynamics with electronic friction has been used to model the effect of electron-hole pair excitation. Most applications are still based on potential energy surfaces (PESs) or forces computed with density functional theory (DFT), using a density functional within the generalized gradient approximation to the exchange-correlation energy. A new development is the use of a semi-empirical version of DFT (the specific reaction parameter (SRP) approach to DFT). We also discuss the accurate methods that have become available to represent electronic structure data for the molecule-surface interaction in global PESs. It has now become possible to describe highly activated H2 + metal surface reactions with chemical accuracy using the SRP-DFT approach, as has been shown for H2 + Cu(111) and Cu(100). However, chemical accuracy with SRP-DFT has yet to be demonstrated for weakly activated systems like H2 + Ru(0001) and non-activated systems like H2 + Pd(111), for which SRP DFs are not yet available. There is now considerable evidence that electron-hole pair (ehp) excitation does not need to be modeled to achieve the (chemically) accurate calculation of dissociative chemisorption and scattering probabilities. Dynamics calculations show that phonons can be safely neglected in the chemically accurate calculation of sticking probabilities on cold metal surfaces for activated systems, and in the calculation of a number of other observables. However, there is now sufficient evidence to suggest that the decision on whether or not to neglect phonons should be taken with care, with appropriate consideration of the observable to be computed and of the relevant surface temperature. AIMD calculations have provided valuable insights into the mechanisms that are operative in the dissociative adsorption and absorption of hydrogen on/in precovered metal surfaces. Classical and quantum dynamics calculations have shown that the reaction probability of H2 on Pt surfaces consisting of (100) steps and (111) terraces can to a very good approximation be computed as a weighted average of the reactivities on the steps and terraces. Progress obtained with dynamics calculations on the scattering of H2 from alloys and from simple low index metal surfaces is also reported. Insights that may be obtained on the reactivity of a metal surface from the prominent presence of out-of-plane diffraction or, conversely, the complete absence of diffraction, are discussed. A new field has been opened up by experiments on H2 scattering from surfaces at fast graz...

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“…All calculations below refer to t el ¼ 2 fs. The dependence of the results on different choices for t el and the potential shift parameter D was discussed in Refs [21,22].…”

Section: The Excited-state Potential and Electronic Lifetimementioning

confidence: 99%

“…This chapter focuses on a comparison of various methods and models to treat FLinduced photochemistry at metal surfaces theoretically. In particular, we will consider DIMET of H 2 and D 2 from Ru(0001), which has been studied experimentally in Refs [12,18,19], and theoretically in Refs [20] and [21,22]. While our analysis is presented only for a specific system and reaction, it is expected to be relevant also for other FL-induced reactions at metal surfaces [23].…”

mentioning

confidence: 99%

Theory of Femtochemistry at Metal Surfaces: Associative Molecular Photodesorption as a Case Study

Saalfrank

Klamroth

Vazhappilly

et al. 2010

Dynamics at Solid State Surfaces and Interfaces

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Reactions on surfaces are of great scientific interest because of their diverse applications. Well-known examples are the production of ammonia on metal surfaces for fertilizers and reduction of poisonous gases from automobiles using catalytic converters [1]. For these applications, metal surfaces -most notably, those consisting of transition metals -are particularly interesting as they offer a great variety of electronic structure and, therefore, tunability toward specific targets.Photoinduced reactions at surfaces were also studied in detail [2][3][4][5]. These are useful, for example, for photocatalysis and nanostructuring of surfaces. Some of these reactions are occurring on femtosecond (1 fs ¼ 10 À15 s) timescale [6]. The advent of femtosecond lasers -that is, ultrashort and intense laser pulses -offers the possibility to monitor these motions in real time, for example, by two-pulse correlation techniques. Moreover, femtochemistry at metal surfaces can be very distinct -on quantitative and qualitative scales -from more traditional surface photochemistry driven by conventional light sources [5,6].Photochemistry at metal surfaces may or may not proceed indirectly, that is, by initial excitation of the substrate electrons rather than by direct excitation of the adsorbate. One way to distinguish between the direct or the substrate-mediated route is through a dependence (direct) [7], or lack thereof (substrate mediated) [8,9], of the reaction cross section on the polarization of the incoming light. In particular for initiating photons in the UV/vis regime, which can deeply penetrate into metal surfaces [10], indirect mechanisms have been suggested to be operative in many cases. Further, when femtosecond lasers (FLs) are used, hot metal electrons that are attached to the adsorbate are believed to often trigger the reaction rather than phonons [6, 11] (see below). For the reaction of interest below, photodesorption of H 2 from Ru(0001), experiments suggest a substrate-mediated, hot-electron-driven mechanism [12].The indirect, substrate-mediated excitation can also be categorized according to its fluence dependence. For the prototypical case of photodesorption, for example,

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Vibrationally enhanced associative photodesorption of molecular hydrogen from Ru(0001)

Cited by 20 publications

References 60 publications

Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations

Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations

Quantum and classical dynamics of reactive scattering of H₂ from metal surfaces

Theory of Femtochemistry at Metal Surfaces: Associative Molecular Photodesorption as a Case Study

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Vibrationally enhanced associative photodesorption of molecular hydrogen from Ru(0001)

Cited by 20 publications

References 60 publications

Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations

Diffusion Rates for Hydrogen on Pd(111) from Molecular Quantum Dynamics Calculations

Quantum and classical dynamics of reactive scattering of H2 from metal surfaces

Theory of Femtochemistry at Metal Surfaces: Associative Molecular Photodesorption as a Case Study

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Product

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Quantum and classical dynamics of reactive scattering of H₂ from metal surfaces