Non-Arrhenius surface temperature dependence in vibrational excitation of NO on Au(1 1 1): possible evidence for the importance of surface electronic states

We report the surface temperature dependence for Δv=+1 vibrational excitation of NO(v=2) due to collisions with Au(1 1 1) at two incidence energies. This is compared to previous measurements on Ag(1 1 1) and Cu(1 1 0). The standard model for electron hole pair mediated vibrational excitation predicts that all three metals will exhibit a nearly Arrhenius temperature dependence with the same effective activation energy. While scattering on Ag(1 1 1) and Cu(1 1 0) obey this prediction, our new results show that the temperature dependence is non-Arrhenius on Au(1 1 1). We suggest that the large spin–orbit interaction present for Au(1 1 1) surface states may be important for vibrational excitation.