Observation of orientational influences on vibrational energy transfer at metal surfaces: Rotational cooling associated with vibrational relaxation at a metal surface

The degree of rotational excitation resulting from collisions of NO(v = 0) and NO(v = 2) with a Au(1 1 1) surface is smaller for NO(v = 2) that undergoes vibrational relaxation, NO(v = 2 → v = 1), than it is for NO that scatters in a vibrationally elastic channel, NO(v = 2 → v = 2) or NO(v = 0 → v = 0). The rotational excitation is less for the vibrational relaxation channel, despite the fact that vibrational relaxation releases 0.25 eV that is potentially available for increased rotational excitation. This difference in amount of rotational excitation for vibrationally inelastic and elastic channels increases with the kinetic energy, Ei, of the incident NO molecules. These observations should provide useful comparisons to full dimensional theories of surface interactions.