Energy redistribution among internal states of nitric oxide molecules upon scattering from Pt(111) crystal surface

The internal states distributions rotation and vibration of nitric oxide molecules scattered from the Pt(111) crystal surface are reported. These distributions were measured as a function of crystal temperature (T_s) and scattering angles. The extent of equilibration of the three degrees of freedom, e.g., translation, rotation, and vibration with the metal surface is discussed in terms of the energy accommodation coefficients γ. It was found that γ_trans>γ_vib>γ _rot. A model is suggested to account for the cold rotational distribution of molecules scattered via a trapping desorption mechanism. The vibrational distributions are determined by kinetic effects and by the competition between vibrational excitation of the adsorbed molecules and their desorption.