Observation of Direct Vibrational Excitation in Gas-Surface Collisions: NO on Ag(111)

Abstract

Vibrationally excited NO molecules have been observed in the scattering of $\mathrm{NO}(v=0)$ from Ag(111). A direct mechanism is inferred based on the observation of $v=1$ angular distributions, which are quasispecular, and rotational-state distributions, which depend on beam energy. Vibrational excitation is found to depend strongly on surface temperature, ${T}_{S}$, and relatively weakly on incident kinetic energy, $E$, reaching (\ensuremath{\sim}7\ifmmode\pm\else\textpm\fi{}5)% at ${T}_{S}=760$ K and $E=120$ kJ ${\mathrm{mol}}^{\ensuremath{-}1}$. These results are discussed in terms of an electronic mechanism for vibrational excitation.