The dissipation of vibrational quanta in exoergic surface processes and its impact on reaction rates: A case study

The kinetic model of exoergic surface reactions developed in a previous contribution [M. Tomellini, Surf. Sci. 577 (2005) 200] has been extended to include multiquantum processes of vibrational energy transfer to the solid. It is shown that, under quasi-steady state conditions, the flux of adsorbing atoms leads to overpopulation of the adatom vibrational ladder with respect to the Boltzmann distribution and to enhanced recombination rates. By means of the associative model for adatom recombination, the vibrational populations have been estimated from experimental data on the kinetics of D-adatoms abstraction by gas H-atoms at Pt(1 1 1), Pt(1 1 0), Ni(1 0 0) and Cu(1 1 1) surfaces. These populations have been found to be hyperthermal and the shape of the energy distribution functions approximated by the Treanor equation. The impact of the interplay between energy dissipation and diatom formation on the reaction rate, has also been analysed and discussed.