Hyperthermal Energy Distribution Functions of the Adspecies in Recombinative Adsorption at Catalytic Surfaces and Their Relevance to ‘Hot Atom’ Reactions

We report on the modeling of the energy distribution functions of the adspecies in diatom formation at catalytic surfaces under steady state conditions. To this end master equations are employed, in the case of either continuous or discrete set of adatom energy levels in the adsorption potential well, and the impact of the distribution function on reaction rate investigated. The transition from thermal to hyperthermal reaction rates has been studied as a function of rate coefficients for recombination and energy dissipation processes. Experimental data available from the literature, have been analysed in the framework of the theoretical model. It is shown that hyperthermal energy distribution functions entail a “hot atom” reaction mechanism.