Vibrational heating in electron stimulated desorption of CO from transition metals: a classical mechanics analysis

The vibrational population inversion in CO molecules desorbed following electron bombardment of transition metal surfaces is modelled with classical mechanics for a bimodal, two-state model. An excited state potential energy surface obtained from DFT cluster calculations for a doubly excited molecule is modified to examine the effects on the vibrational state resolved desorption probabilities. An interplay of factors is found to determine these probabilities: the potential energy gained from electronic excitation of the molecule, the kinetic energy gained from propagation on the excited state, and the potential energy at the point of relaxation to the electronic ground-state. Within the limited dimensionality of the model, the DFT PES gives a good reproduction of the experimental findings concerning the vibrational population inversion, the translational energy of the desorbing molecules and the positive correlation between vibrational state and translational energy.