TY - GEN
T1 - Chemisorbed-molecule potential-energy surfaces and electronically stimulated processes
AU - Jennison, Dwight R.
AU - Stechel, Ellen B.
AU - Burns, Alan R.
AU - Li, Y. S.
PY - 1994
Y1 - 1994
N2 - 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.
AB - 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.
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M3 - Conference contribution
AN - SCOPUS:0028742545
SN - 0819414182
T3 - Proceedings of SPIE - The International Society for Optical Engineering
SP - 192
EP - 206
BT - Proceedings of SPIE - The International Society for Optical Engineering
A2 - Dai, Hai-Lung
A2 - Sibener, Steven J.
PB - Society of Photo-Optical Instrumentation Engineers
T2 - Laser Techniques for Surface Science
Y2 - 27 January 1994 through 29 January 1994
ER -