Chemisorbed-molecule potential energy surfaces and DIET processes

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Beam interactions with materials and atoms, 1995-06, Vol.101 (1), p.22-30
• Main Authors: Jennison, D.R., Stechel, E.B., Burns, A.R., Li, Y.S.
• Format: Article
• Language: English
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/0168-583X(95)00292-8

We report the use of the local-density approximation, with and without gradient corrections, for the calculation of ground-state potential energy surfaces (PESs) for chemisorbed molecules. We focus on chemisorbed NO and ammonia on Pd(1 1 1) and compare our results with the latest experimental information. We then turn to two aspects of excited-state PESs. First, we compare first-principles calculations of the forces on an ammonia ion as a function of distance from the surface. We find that the image-charge model fails significantly at distances which are the most relevant for dynamics, closer than ∼3 Å, and discuss reasons for the failure. We then summarize a purely electronic adiabatic model of the moleuule-surface bond and use empirical parameters to estimate hot carrier-produced excited states of chemisorbed NO. We find multiple PESs and a novel interpretation of the π ∗ resonance, seen in inverse photoemission.