Abstract
We have developed an instrument that uses photolysis of hydrogen halides to produce nearly monoenergetic hydrogen atom beams and Rydberg atom tagging to obtain accurate angle-resolved time-of-flight distributions of atoms scattered from surfaces. The surfaces are prepared under strict ultrahigh vacuum conditions. Data from these experiments can provide excellent benchmarks for theory, from which it is possible to obtain an atomic scale understanding of the underlying dynamical processes governing H atom adsorption. In this way, the mechanism of adsorption on metals is revealed, showing a penetration–resurfacing mechanism that relies on electronic excitation of the metal by the H atom to succeed. Contrasting this, when H atoms collide at graphene surfaces, the dynamics of bond formation involving at least four carbon atoms govern adsorption. Future perspectives of H atom scattering from surfaces are also outlined.
Highlights
Since the discovery of quantum mechanics nearly 100 years ago, the underlying physical laws governing chemistry have been known, but the computational implementation of those laws has remained completely intractable
A common strategy is to pick one of the elementary steps of the process and study it on a well-defined model system, an approach suggested by Langmuir as early as 192794 and pioneered by Ertl.[95−97] Experiments on the inelastic scattering of atoms and molecules from well-defined surfaces under ultrahigh vacuum conditions allow us to probe the mechanisms of dissipation in great detail, addressing fundamental questions related to adsorption,[98] desorption,[99] diffusion, and reactivity;[100] in short, these are all of the elementary steps needed for surface chemistry to take place
Inspired by work in gas phase chemical dynamics, we have recently developed a new experimental tool to study inelastic H atom scattering from solid surfaces.[131]
Summary
Since the discovery of quantum mechanics nearly 100 years ago, the underlying physical laws governing chemistry have been known, but the computational implementation of those laws has remained completely intractable. A common strategy is to pick one of the elementary steps of the process and study it on a well-defined model system, an approach suggested by Langmuir as early as 192794 and pioneered by Ertl.[95−97] Experiments on the inelastic scattering of atoms and molecules from well-defined surfaces under ultrahigh vacuum conditions allow us to probe the mechanisms of dissipation in great detail, addressing fundamental questions related to adsorption,[98] desorption,[99] diffusion, and reactivity;[100] in short, these are all of the elementary steps needed for surface chemistry to take place Based on such experiments, new theoretical models can be developed and tested that accurately describe the delicate interplay between electronic and nuclear motion in prototypical chemical reactions, a capability that is necessary for accurate predictions of reaction rates in heterogeneous catalysis. The paper concludes with a section describing new ideas and future possible research directions
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