Chemisorbed-molecule potential-energy surfaces and electronically stimulated processes

Dwight R. Jennison; Ellen B. Stechel; Alan R. Burns; Y. S. Li

doi:10.1117/12.180847

21 July 1994 Chemisorbed-molecule potential-energy surfaces and electronically stimulated processes

Dwight R. Jennison, Ellen B. Stechel, Alan R. Burns, Y. S. Li

Proceedings Volume 2125, Laser Techniques for Surface Science; (1994) https://doi.org/10.1117/12.180847
Event: OE/LASE '94, 1994, Los Angeles, CA, United States

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.

Citation Download Citation

Dwight R. Jennison, Ellen B. Stechel, Alan R. Burns, and Y. S. Li "Chemisorbed-molecule potential-energy surfaces and electronically stimulated processes", Proc. SPIE 2125, Laser Techniques for Surface Science, (21 July 1994); https://doi.org/10.1117/12.180847

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