Eley Rideal recombination of hydrogen atoms on Cu(111): Quantitative role of electronic excitation in cross sections and product distributions

Abstract

Eley-Rideal (ER) reaction between a projectile and an adsorbate at a gas-surface interface represents many interesting dynamic features. Electron-hole pairs (EHPs) could play an important role in this process, given the interaction between the accelerated incident atom/molecule and the surface electrons. Here, we examine the EHP effects in a benchmark ER reaction of an impinging H/D atom and pre-covered D/H atoms on Cu(111) by ab initio molecular dynamics simulations. It is found that energy dissipation to EHPs lowers the reaction cross sections by ∼1/3, mainly due to the suppression of the hot atom mechanism, but has a minor effect on rotational distributions, leading to quantitative agreement with experimental data. More interestingly, electronic excitation is responsible for the isotopic effect in translational energy distributions, but probably not for that in angular distributions. Our results highlight the specific role of electronic excitation in detailed dynamic quantities in the ER process.