Vibrational excitation and deexcitation rates of molecules adsorbed on metal surfaces

The rates for vibrational excitation and deexcitation of adsorbed molecules on metal surfaces are reported. The desorption of the adsorbed molecules is shown to compete with the excitation process, resulting in "vibrationally cold" desorbing molecules. Simple rate equations, together with the available experimental data, are used to estimate the rates for vibrational excitation and deexcitation of NO molecules on Pt(111) surfaces as a function of the crystal temperature. The application of this approach to other systems is discussed.