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Proceedings Paper

Chemisorbed-molecule potential-energy surfaces and electronically stimulated processes
Author(s): Dwight R. Jennison; Ellen B. Stechel; Alan R. Burns; Y. S. Li
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Paper Abstract

Three topics illustrate some central physics of processes produced by UV-laser and low-energy electron stimulation. First, a multi-dimensional ground-state potential energy surface (PES) for NH3:Pd(111), computed using ab initio local-density functional theory, allows dramatically different dynamics depending on poorly-known excited-state forces. We use quantum- resolved experimental data to argue that stimulated desorption is dominated by a direct path off the surface, following placement of the wavepacket on a molecule-surface hard wall accessed by internal molecular motion. This illustrates the questionable relevance of 1D models for understanding molecule-surface dynamics. Second, we study the image-charge model of excited state forces experienced by ions produced, for example, by hot carrier attachment. Ab initio results show that this model totally fails at molecule-surface distances typical of chemisorption. Finally, we present a purely-electronic adiabatic model of excited state PESs and use it to argue that, if significant covalent interactions occur between an adsorbate and a surface, hot carrier attachment does not simply produce singly- charged ions. Instead, attachment creates excitation of the molecule-surface bond occur and, in some cases, may result in multiply-charged ions.

Paper Details

Date Published: 21 July 1994
PDF: 15 pages
Proc. SPIE 2125, Laser Techniques for Surface Science, (21 July 1994); doi: 10.1117/12.180847
Show Author Affiliations
Dwight R. Jennison, Sandia National Labs. (United States)
Ellen B. Stechel, Sandia National Labs. (United States)
Alan R. Burns, Sandia National Labs. (United States)
Y. S. Li, Biosym Technologies, Inc. (United States)

Published in SPIE Proceedings Vol. 2125:
Laser Techniques for Surface Science
Hai-Lung Dai; Steven J. Sibener, Editor(s)

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