Probing Gas-surface Potential Energy Surfaces with Diffraction of Hydrogen Molecules

Abstract

We review recent experiments where diffraction of deuterium molecules from single-crystal surfaces was employed to characterize the potential energy surface for hydrogen dissociative chemisorption. Scattering experiments were carried out on Cu (001), which is the prototype of a system with a high barrier for dissociative chemisorption, on Ni (110), which is the prototype of a system with a low barrier, and on NiAl(110), which is the prototype of an alloy surface with a high barrier. The experiments were carried out on two different set-ups at incident energies between about 20 and 250 meV. Elastic and rotationally inelastic diffraction (RID) peaks were observed in all experiments. Diffraction probabilities are presented and compared for each surface. Elastic diffraction intensities were interpreted with a simple corrugated hard wall scattering potential. The values of the corrugation are h = 0.075 Å for D2/Cu (001), and h = 0.091 Å for D2/Ni (110). A satisfactory fit of the diffraction intensities could be obtained for D2/NiAl(110) only over a very limited range of incident beam energies. A major finding of our experiments is that dissociative chemisorption strongly affects RID probabilities. These are higher by about a factor of 3-5 for scattering from Ni (110) than for the high-barrier systems Cu (001) and NiAl(110). The high rotational transition probability for systems with low barrier is interpreted as a consequence of the angular anisotropy of the chemisorption potential. Perspectives for future experiments are discussed.

Department(s)

Physics

International Standard Serial Number (ISSN)

0953-8984

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2024 IOP Publishing, All rights reserved.

Publication Date

24 Jun 2002

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