American Chemical Society
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Quantum Stereodynamics of H2 Scattering from Co(0001): Influence of Reaction Channels

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journal contribution
posted on 2019-06-10, 00:00 authored by Marcos del Cueto, Xueyao Zhou, Alberto S. Muzas, Cristina Díaz, Fernando Martín, Bin Jiang, Hua Guo
Diffraction of light molecules from crystalline surfaces is known to provide useful insights into surface topology and molecule/surface interaction. It has been even suggested that molecular diffraction could be used to obtain relevant information about dissociative chemisorption. However, such a direct connection between the diffracted molecules and reactive channels has not been clearly established to date. Because of its low barrier, dissociative chemisorption H2 on Co(0001) provides an ideal testing ground for examining the influence of reactive channels on diffraction and rotational inelastic scattering of molecules from the surface. Here, we report quantum state-to-state scattering dynamics of aligned H2 from Co(0001) using time-dependent quantum dynamical methods on a full-dimensional potential energy surface determined from first-principles calculations. Our results show that the ΔmJ ≠ 0 type rotational inelastic scattering depends on the initial alignment (mJi) of the impinging molecule. The origin of this steric effect was uncovered by quasi-classical trajectory calculations, which show that the ΔmJ ≠ 0 events are substantially enhanced by “quasi-reactive” trajectories that access the dissociative channel, characterized by classical turning points that are close to the surface with elongated H2 interatomic distances. This correlation is further confirmed by reduced-dimensional quantum calculations of the same system but with a fixed H2 bond, which exhibit a significant reduction of ΔmJ ≠ 0 type transitions, due apparently to the inability of H2 to elongate and dissociate. This theoretical investigation suggests that the impact of reactive channels can be probed by scattering of aligned molecules from reactive metal surfaces.