Energy disposal in collisions of nitric oxide with molecular adlayers on transition metal single crystal surfaces: Translational energy disposal

Abstract

The dynamics of the scattering of nitric oxide (NO) from well-characterized and ordered layers of carbon monoxide (CO) and ethylidyne (CCH3) adsorbed on a Pt(111) substrate have been investigated by time-of-flight methods. Time-of-flight profiles for scattered NO are reported for a range of incident NO translational energies between 10 and 50 kJ mol−1 from scattering substrates at 108 and 300 K. The measurements reveal that scattering occurs both into a trapping-desorption channel and a direct inelastic channel. The latter is accompanied by a significant (>60%) loss in the NO translational energy. This is true for both substrates and contrasts markedly with the many observations made of atomic and molecular scattering from clean metal single crystal planes. Hard cube model calculations are presented as a basis for the interpretation of the direct inelastic behavior that point toward a surface collision partner mass of the same magnitude as the incident molecule and toward differences in the strength of the NO-adlayer attractive interaction as the origin of subtle changes in the scattering behavior from the low temperature substrates as a function of the incident translational energy.