The interaction of highly vibrationally excited molecules with surfaces: vibrational relaxation and reaction of NO(v) at Cu(111) and O/Cu(111)

We have studied the reaction and inelastic scattering of ground and vibrati onally excited NO on Cu(111). We employed laser-based techniques to prepare NO in vibrationally excited states, stimulated emission pumping (SEP) to p repare v=13 and v=15 and infrared overtone pumping to prepare v=2. Laser io nization detection schemes were developed for probing the state distributio n of highly vibrationally excited NO molecules. Ground-state NO(v=0) dissoc iates at Cu(111) with a probability of approximate to 2x10(-4), with little dependence on the translational energy in the range between 29 and 65 kJ m ol(-1). The dissociation probability is strongly enhanced by vibrational ex citation to v=13 and 15. The dissociation continues until the oxygen covera ge on Cu(111) reaches saturation. For highly excited NO(v=13, 15) scatterin g from O/Cu(111), we have seen efficient multi-quantum relaxation (up to De lta v=-5). For NO(v=2), in contrast, the survival probability is nearly 90% . Measurements of the translational and rotational state distributions afte r scattering support a direct-inelastic mechanism for vibrational relaxatio n, with strong flow of energy into the surface. The branching ratios for vi brational relaxation are independent of the kinetic energy in our experimen ts.