Abstract
We describe a method to obtain absolute vibrational excitation probabilities of molecules scattering from a surface based on measurements of the rotational state, scattering angle, and temporal distributions of the scattered molecules and apply this method to the vibrational excitation of NO scattering from Au(111). We report the absolute excitation probabilities to the v = 1 and v = 2 vibrational states, rotational excitation distributions, and final scattering angle distributions for a wide range of incidence energies and surface temperatures. In addition to demonstrating the methodology for obtaining absolute scattering probabilities, these results provide an excellent benchmark for theoretical calculations of molecule-surface scattering.
Highlights
A fundamental molecular level insight into the underlying dynamics of energy exchange between molecules and metal surfaces is a vital prerequisite to a comprehensive theory of gas-surface chemistry, bearing on subjects ranging from corrosion and electrochemistry to heterogeneous catalysis
The ample evidence of energy exchange between molecular vibrations and metallic electron-hole pairs (EHP) gained from molecular beam-surface scattering experiments includes studies of vibrational excitation,8,9,12 vibrational relaxation,4,28 and electron emission5,6,29 occurring in the course of molecule-surface encounters
The experimental protocol presented in this work is employed to determine absolute vibrational excitation probabilities for both the fundamental, NO(v = 0→1), and first overtone transition, NO(v = 0→2), when NO is scattered from a Au(111) surface at six different incidence energies, Ei, from 0.11 eV to 1.05 eV at surface temperatures, TS, ranging from 300 K to 1000 K. These results provide an extensive benchmark dataset that probes the EHP-V coupling for this system suitable for comparison with theories of electronically nonadiabatic interactions in molecule surface collisions
Summary
A fundamental molecular level insight into the underlying dynamics of energy exchange between molecules and metal surfaces is a vital prerequisite to a comprehensive theory of gas-surface chemistry, bearing on subjects ranging from corrosion and electrochemistry to heterogeneous catalysis. Molecular beam-surface scattering experiments combined with laser based methods of preparation and detection enable control over orientation, velocity, and the internal state of the gaseous collision partner, and produce experimental results that can be directly compared to high-level theoretical calculations. The ample evidence of energy exchange between molecular vibrations and metallic EHPs gained from molecular beam-surface scattering experiments includes studies of (single and multi-quantum) vibrational excitation, (single and multi-quantum) vibrational relaxation, and electron emission occurring in the course of molecule-surface encounters. Vibrational excitation exhibiting an Arrhenius-like surface temperature dependence with activation energy equal to the vibrational excitation energy is often considered to be a signature a)Author to whom correspondence should be addressed
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