Quasi-elastic helium-atom scattering from surfaces: experiment and interpretation

• Published in: Journal of physics. Condensed matter Vol. 14; no. 24; pp. 6173 - 6191
• Main Authors: Jardine, A P, Ellis, J, Allison, W
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Bristol IOP Publishing 24.06.2002; Institute of Physics
• Subjects: Applied sciences; Atom, molecule, and ion scattering; Atomic, molecular, and ion beam impact and interactions with surfaces; Chemistry; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Diffusion; interface formation; Electron and ion emission by liquids and solids; impact phenomena; Exact sciences and technology; General and physical chemistry; Impact phenomena (including electron spectra and sputtering); Metals. Metallurgy; Other methods of structure determination; Physics; Solid surfaces and solid-solid interfaces; Solid-gas interface; Structure of solids and liquids; crystallography; Surface and interface chemistry; Surface physical chemistry; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Inorganic adsorbate; Helium Atoms; Inorganic compounds; Quasi-elastic scattering; Surface diffusion; Energy barrier; Gas solid adsorption; Reviews; Dynamics; Transition elements; Gas solid interface; Metallic adsorbent; Carbon monoxide; Copper; Atom scattering; Diffusion
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/14/24/315

Diffusion of an adsorbate is affected both by the adiabatic potential energy surface in which the adsorbate moves and by the rate of thermal coupling between the adsorbate and substrate. In principle both factors are amenable to investigation through quasi-elastic broadening in the energy spread of a probing beam of helium atoms. This review provides a topical summary of both the quasi-elastic helium-atom scattering technique and the available data in relation to the determination of diffusion parameters. In particular, we discuss the activation barriers deduced from experiment and their relation to the adiabatic potential and the central role played by the friction parameter, using the CO /Cu(001) system as a case study. The main issues to emerge are the need for detailed molecular dynamics simulations in the interpretation of data and the desirability of significantly greater energy resolution in the experiments themselves. [Also discussed: self-diffusion of Pb, Ni, and Ag; S/Cu; H and D on Pt; Xe/Pt; Na/Cu; Ge/Ge; CO/Ni.]