Vibrationally inelastic collisions of H+D2: A comparison of quantum mechanical, quasiclassical, and experimental results

Jambrina, Pablo G.; Aldegunde, J.; Castillo, J. F.; Aoiz, F. J.; Rábanos, V. Sáez

doi:10.1063/1.3065668

Cited by 5 publications

(3 citation statements)

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“…It is even more so for the H-D 2 inelastic collisions that have been the object of very few studies. Indeed, the vibrational excitation of D 2 by H has been the object of little experimental and theoretical works [2][3][4] and no recent studies on the pure rotational excitation of D 2 by H has been performed.…”

Section: Introductionmentioning

confidence: 99%

Communication: The rotational excitation of D2 by H: On the importance of the reactive channels

Lique

Fauré

2012

The Journal of Chemical Physics

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We report fully-quantum time-independent calculations of cross sections and rate coefficients for the collisional excitation and dissociation of D(2) by H, two astrophysically relevant processes. Our calculations are based on the recent H(3) global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)]. Results of exact three-dimensional calculations, i.e., including the reactive channels, are compared to pure inelastic two-dimensional calculations based on the rigid rotor approximation. A reasonable agreement is found between the two sets of inelastic cross sections over the whole energy range 10-9000 cm(-1). At the highest collisional energies, where the reactive channels are significant, the rigid rotor approach slightly overestimates the cross sections, as expected. At moderate collisional energies, however, the opposite behaviour is observed. The rigid rotor approach is found to be reliable at temperatures below ~500 K, with a significant but moderate contribution from reactive channels.

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Section: Introductionmentioning

confidence: 99%

Communication: The rotational excitation of D2 by H: On the importance of the reactive channels

Lique

Fauré

2012

The Journal of Chemical Physics

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“…This dynamics is similar to that of the tug-of-war mechanism observed in the gas phase collision of H and D 2 (6,7,147). In commonly accepted mechanisms, the vibrational excitation of molecules in gas phase collisions occurs via compressing the bond.…”

Section: The Fast Component: Atoms Scattering On a Corrugated Surfacesupporting

confidence: 73%

Dynamics of Hydrogen Atoms Scattering from Surfaces

Jiang¹

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Hydrogen atoms interactions with single crystal surfaces are the simplest processes in surface science, which are of both practical and fundamental interest. Chemical reactions of hydrogen atoms with single crystal surfaces lead to adsorption. Despite the fact that it has been studied for decades, the dynamics of hydrogen atom adsorption is still not fully understood. Adsorption involves the impinging hydrogen atom losing its initial translational energy and dissipating the energy of the chemical bond formed with the surface. How hydrogen atoms dissipate their initial translational energy to adsorb on a surface is still an open question. In principle, a hydrogen atom may lose its initial translational energy to the vibrations of the surface atoms or to electron-hole pair excitations. To answer this question in detail, a state-of-the-art UHV machine was built to study atom-surface scattering. During my doctoral study, I conducted experiments on hydrogen atom scattering from single crystal surfaces, including Au(111) and Pt(111), Xe covered Au( 111) and epitaxial graphene on Pt(111). High resolution scattering angle resolved translational energy loss distributions have been obtained. The goal of this research is to achieve a detailed understanding of the mechanisms of H atom interaction with different kinds of single crystal surfaces, and especially of the translational energy transfer between the atom and the surfaces, which is fundamentally important to the adsorption processes.To compare hydrogen atom translational energy loss to metals and insulators, I studied scatterings of hydrogen atoms from Au(111) and Xe layer on Au(111). Hydrogen atoms scattering from insulating Xe layer exhibit a small energy loss and a narrow translational energy distribution and can be understood using a binary collision model. In contrast, Hydrogen atoms scattering from Au(111) show a large energy loss and a broad translational energy distribution, indicating that a broad continuum of accepter states in the solid contribute to the translational energy loss. A MD simulation self-consistently including the non-adiabatic electronic excitations agrees with the experiments of hydrogen atom scattering on metal. In contrast, calculations neglecting the electronic excitations cannot capture the essence of the measurements, indicating hydrogen atoms scattering from metal is strongly non-adiabatic. Exchanging H atoms with D atoms only leads to minor change in the translational energy loss distribution. This is explained by a cancellation effect, where the phonon excitation is enhanced for D but the electron-hole pair excitation is reduced.To study the dynamics of chemically activated adsorption of hydrogen atoms, I did a series of experiments on hydrogen atoms scattering from epitaxial graphene, which has a barrier to C-H bond formation of several hundreds of meV. The scattered hydrogen atoms exhibit a bimodal distribution for translational energy and scattering angle. The fast component in the distribution originates from atoms scattered back...

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“…It is well-known that recrossing plays an important role at high enough energies contributing to a considerable decrease of the reactivity. 38,50 As discussed in section 2.2, recrossing takes place when a trajectory crosses the same transition state an even number of times, in such a way that it ends up being inelastic. Recrossing can be easily quantified through QCT calculations, whose reliability for the present study has been already established in Figures 2 and 4.…”

Section: Resultsmentioning

confidence: 99%

Influence of the Reactants Rotational Excitation on the H + D₂(v = 0, j) Reactivity

et al. 2015

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We have analyzed the influence of the rotational excitation on the H+D 2 (υ=0, j) reaction through quantum mechanical (QM) and quasiclassical trajectories (QCT) calculations at a wide range of total energies. The agreement between both types of calculations is excellent. We have found that the rotational excitation largely increases the reactivity at large values of the total energy. Such increase cannot be attributed to a stereodynamical effect but to the existence of recrossing trajectories that become reactive as the target molecule gets rotationally excited. At low total energies, however, recrossing is not significant and the reactivity evolution is dominated by changes in the collision energy; the reactivity decreases with the collision energy as it shrinks the acceptance cone. When state-to-state results are considered, rotational excitation leads to cold product's rovibrational distributions, so that most of the energy is released as recoil energy.

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Vibrationally inelastic collisions of H+D2: A comparison of quantum mechanical, quasiclassical, and experimental results

Abstract: A general intermolecular force field based on tight-binding quantum chemical calculations

Cited by 5 publications

References 18 publications

Communication: The rotational excitation of D2 by H: On the importance of the reactive channels

Communication: The rotational excitation of D2 by H: On the importance of the reactive channels

Dynamics of Hydrogen Atoms Scattering from Surfaces

Influence of the Reactants Rotational Excitation on the H + D₂(v = 0, j) Reactivity

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Vibrationally inelastic collisions of H+D2: A comparison of quantum mechanical, quasiclassical, and experimental results

Abstract: A general intermolecular force field based on tight-binding quantum chemical calculations

Cited by 5 publications

References 18 publications

Communication: The rotational excitation of D2 by H: On the importance of the reactive channels

Communication: The rotational excitation of D2 by H: On the importance of the reactive channels

Dynamics of Hydrogen Atoms Scattering from Surfaces

Influence of the Reactants Rotational Excitation on the H + D2(v = 0, j) Reactivity

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Influence of the Reactants Rotational Excitation on the H + D₂(v = 0, j) Reactivity