Inverse Velocity Dependence of Vibrationally Promoted Electron Emission from a Metal Surface

N. H. Nahler, J. D. White, J. LaRue, D. J. Auerbach, A. M. Wodtke
2008 Science  
All previous experimental and theoretical studies of molecular interactions at metal surfaces show that electronically nonadiabatic influences increase with molecular velocity. Here, we report the observation of a nonadiabatic electronic effect that follows the opposite trend: the probability for electron emission from a low work function surface -Au(111) capped by half a monolayer of Cs -increases as the velocity of the incident NO molecule decreases in the course of collisions with highly
more » ... ationally excited NO(X 2 Π½, V=18), reaching 0.1 at the lowest velocity studied. We show these results are consistent with a vibrational auto-detachment mechanism, where electron emission is only possible beyond a certain critical distance from the surface. This outcome implies that important energy dissipation pathways involving nonadiabatic electronic excitations and furthermore not captured by present theoretical methods, may influence reaction rates at surfaces.
doi:10.1126/science.1160040 pmid:18755972 fatcat:wvvqivmpljfipd7k7e4vp2ilmy