State specific velocity distribution of hydrogen isotopes desorbing from Pd(100)

Schröter, L.; Trame, Chr.; David, Rudolf; Zacharias, H.

doi:10.1016/0039-6028(92)91443-f

Cited by 36 publications

(18 citation statements)

References 14 publications

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“…molecules with low kinetic energy dissociatively adsorb at Pd(100) surfaces with a large initial sticking coefficient 1,6 . The preference of non-activated dissociation pathways for low kinetic energies of the H 2 molecules is also consistent with the independence of the initial sticking coefficient on incident angle Θ as well as with the measured Maxwell-Boltzmann velocity distribution of desorbing H 2 molecules which corresponds to the surface temperature of the palladium substrate 5,7 .…”

Section: Introductionsupporting

confidence: 82%

“…At those larger kinetic energies the dependence of the initial sticking coefficient on the incident angle of the molecules changes into a cos n−1 (Θ) behavior with n increasing up to n ≈ 1.6 for beam energies of 0.4 eV. State resolved desorption experiments show that the occupancy of the first vibrational excitation is significantly higher than that corresponding to a gas of hydrogen molecules in equilibrium with the surface temperature 2,4,5 . This finding is called vibrational heating.…”

Section: Introductionmentioning

confidence: 96%

“…The H 2 / Pd system is particularly interesting as an example of non-activated dissociation over a transition metal surface. The dissociation process has been studied using molecular beam adsorption experiments 1 as well as state resolved time-offlight measurements of desorbing hydrogen molecules [2][3][4][5] .…”

Section: Introductionmentioning

confidence: 99%

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Potential-energy surface forH2dissociation over Pd(100)

1996

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The potential energy surface (PES) of dissociative adsorption of H2 on Pd(100) is investigated using density functional theory and the full-potential linear augmented plane wave (FP-LAPW) method. Several dissociation pathways are identified which have a vanishing energy barrier. A pronounced dependence of the potential energy on "cartwheel" rotations of the molecular axis is found. The calculated PES shows no indication of the presence of a precursor state in front of the surface. Both results indicate that steering effects determine the observed decrease of the sticking coefficient at low energies of the H2 molecules. We show that the topology of the PES is related to the dependence of the covalent H(s)-Pd(d) interactions on the orientation of the H2 molecule.

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Section: Introductionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 96%

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Potential-energy surface forH2dissociation over Pd(100)

1996

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“…The latter product is efficiently ionized and obscures in the arrival time spectrum the signal from directly desorbing H 2 (v = 1, j = 1). 54 In addition to the energy dependent alignment results also the average translational desorption energies E kin can be deduced from this data for each rotational state. As discussed in more detail below, for ground state H 2 molecules the highest E kin = (880 ± 20) meV is observed in j = 1, steadily decreasing to E kin = (630 ± 20) meV for j = 8.…”

Section: A Experimental Resultsmentioning

confidence: 99%

“…54 In this specific realisation, the H 2 + photoions are produced in a three-stage time-of-flight tube to enhance the detection sensitivity, and are detected by microchannel plates. In the first stage, they are slightly (a 1 = 1.25 V/cm) accelerated over a distance of s 1 = 22 mm towards a field-free drift tube of s 2 = 65 mm length.…”

Section: A Desorption Experimentsmentioning

confidence: 99%

Reactive scattering of H2 from Cu(100): Comparison of dynamics calculations based on the specific reaction parameter approach to density functional theory with experiment

Sementa

Wijzenbroek²,

Kolck³

et al. 2013

The Journal of Chemical Physics

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201

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We present new experimental and theoretical results for reactive scattering of dihydrogen from Cu(100). In the new experiments, the associative desorption of H 2 is studied in a velocity resolved and final rovibrational state selected manner, using time-of-flight techniques in combination with resonance-enhanced multi-photon ionization laser detection. Average desorption energies and rotational quadrupole alignment parameters were obtained in this way for a number of (v = 0, 1) rotational states, v being the vibrational quantum number. Results of quantum dynamics calculations based on a potential energy surface computed with a specific reaction parameter (SRP) density functional, which was derived earlier for dihydrogen interacting with Cu (111), are compared with the results of the new experiments and with the results of previous molecular beam experiments on sticking of H 2 and on rovibrationally elastic and inelastic scattering of H 2 and D 2 from Cu(100). The calculations use the Born-Oppenheimer and static surface approximations. With the functional derived semi-empirically for dihydrogen + Cu(111), a chemically accurate description is obtained of the molecular beam experiments on sticking of H 2 on Cu(100), and a highly accurate description is obtained of rovibrationally elastic and inelastic scattering of D 2 from Cu(100) and of the orientational dependence of the reaction of (v = 1, j = 2 − 4) H 2 on Cu(100). This suggests that a SRP density functional derived for H 2 interacting with a specific low index face of a metal will yield accurate results for H 2 reactively scattering from another low index face of the same metal, and that it may also yield accurate results for H 2 interacting with a defected (e.g., stepped) surface of that same metal, in a system of catalytic interest. However, the description that was obtained of the average desorption energies, of rovibrationally elastic and inelastic scattering of H 2 from Cu(100), and of the orientational dependence of reaction of (v = 0, j = 3 − 5, 8) H 2 on Cu(100) compares less well with the available experiments. More research is needed to establish whether more accurate SRP-density functional theory dynamics results can be obtained for these observables if surface atom motion is added to the dynamical model. The experimentally and theoretically found dependence of the rotational quadrupole alignment parameter on the rotational quantum number provides evidence for rotational enhancement of reaction at low translational energies.

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Rotational Dynamics in Associative Desorption of Hydrogen from Pd(100) and Cu(111) Surfaces

Wetzig

Rutkowski

Zacharias

1997

phys. stat. sol. (a)

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The rotational dynamics in associative desorption of hydrogen from an s‐metal and a transition metal surface is state‐selectively investigated by resonantly enhanced two‐photon ionization and by laser induced fluorescence. From these measurements rotational state populations, state‐selective velocity distributions, and the spatial alignment of the rotational angular momentum can be deduced. Recently, fully six‐dimensional potential energy surfaces (PES) have been developed for this reaction on both substrates which allow quantum mechanical simulations of the dynamics. First calculations provide a comparison with the experimental data. The different chemical nature of palladium and copper is reflected in the rotational state population, the coupling of rotation to other degrees of freedom, and the spatial alignment of the rotation. For Pd(100) good agreement between theory and experiment is obtained, while for Cu(111) the experimental data suggest that the azimuthal corrugation is significantly higher than assumed in the calculations.

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State specific velocity distribution of hydrogen isotopes desorbing from Pd(100)

Cited by 36 publications

References 14 publications

Potential-energy surface forH2dissociation over Pd(100)

Potential-energy surface forH2dissociation over Pd(100)

Reactive scattering of H2 from Cu(100): Comparison of dynamics calculations based on the specific reaction parameter approach to density functional theory with experiment

Rotational Dynamics in Associative Desorption of Hydrogen from Pd(100) and Cu(111) Surfaces

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