Aart W. Kleyn

Bio: Aart W. Kleyn is an academic researcher from Leiden University. The author has contributed to research in topics: Scattering & Dissociation (chemistry). The author has an hindex of 41, co-authored 218 publications receiving 5759 citations. Previous affiliations of Aart W. Kleyn include Fundamental Research on Matter Institute for Atomic and Molecular Physics & University of Amsterdam.

Chemical Dynamics at the Gas−Surface Interface

Abstract: We review recent progress in the understanding of the chemical dynamics of gas−surface reactions. Such reactions can involve many dynamically distinct interactions. Our review begins by considering a number of these important elementary processes, dealing in turn with (1) the initial gas−surface interaction including translational, rotational, and vibrational energy exchange, the discussion of vibrational interactions covering both direct vibrational excitation and vibrational relaxation at surfaces; (2) the trapping or adsorption of atoms and molecules on the surface; and (3) the important elementary processes of surface diffusion and desorption. We conclude with a detailed look at two examples of gas−surface reactions, first summarizing what is now known about the dissociative chemisorption of hydrogen at Cu surfaces (and the reverse process of recombinative desorption). Then we describe recent studies of direct gas−surface abstraction (or Eley−Rideal) reactions.

Real-Time Observation of Molecular Motion on a Surface

Abstract: The laser-induced movement of CO molecules over a platinum surface was followed in real time by means of ultrafast vibrational spectroscopy. Because the CO molecules bound on different surface sites exhibit different C–O stretch vibrational frequencies, the site-to-site hopping, triggered by excitation with a laser pulse, can be determined from subpicosecond changes in the vibrational spectra. The unexpectedly fast motion—characterized by a 500-femtosecond time constant—reveals that a rotational motion of the CO molecules, rather than pure translation, is required for this diffusion process. This conclusion is corroborated by density functional theory calculations.

Observation of steric effects in gas–surface scattering

Abstract: Molecules adsorbed on a surface are known to show preferential orientations, and in particular, the interaction potential between a linear molecule and a surface depends on the orientation of the molecular axis. But the fact that the molecules eventually adsorbed are orientated with respect to the surface is not evidence that the dynamics of gas–surface interactions is governed by the initial molecular orientation in the gas phase. For example at very low velocities the molecule might achieve its optimum orientation adiabatically during its approach to the surface. Dependence of scattering dynamics on molecular orientation can also be degraded as a result of surface structure and surface vibrations. There have been, experimental studies, however, which suggest that orientational or steric effects could influence gas–surface scattering1–4. Thus, the much larger rotational excitation for NO- than for N2-scattering from Ag(lll) indicates that large anisotropies can occur in a potential for gas–surface dynamics (G. O. Sitz et al. manuscript in preparation). The double rotational rainbow observed in the rotational state distribution for NO/Ag(111) (refs 3 and 4) can also be interpreted as a manifestation of this anisotropy5–9. These studies all indicate that steric effects could be important and here we report on scattering of orientated NO from Ag(111) to provide direct experimental evidence for the importance of such effects in gas–surface interactions.

Electronic structure and catalysis on metal surfaces

Abstract: The powerful computational resources available to scientists today, together with recent improvements in electronic structure calculation algorithms, are providing important new tools for researchers in the fields of surface science and catalysis. In this review, we discuss first principles calculations that are now capable of providing qualitative and, in many cases, quantitative insights into surface chemistry. The calculations can aid in the establishment of chemisorption trends across the transition metals, in the characterization of reaction pathways on individual metals, and in the design of novel catalysts. First principles studies provide an excellent fundamental complement to experimental investigations of the above phenomena and can often allow the elucidation of important mechanistic details that would be difficult, if not impossible, to determine from experiments alone.