Adsorption and isotopic exchange of nitrogen on polycrystalline iron films between 273 and 600 K

The adsorption of nitrogen on evaporated iron films under uhv conditions has been studied between 273 and 600 K by means of direct volumetric and pressure measurements. The dissociative adsorption occurs with sticking probabilities in the range of 10^?8 to 10^?7 and apparent activation energies between ?1 and 5 kJ mol^?1 depending on the structure of the film. A mechanism for the dissociative adsorption of nitrogen is proposed taking into account molecularly adsorbed nitrogen as a precursor. After the adsorption of nitrogen enriched in ¹⁵N₂ the establishing of the iso topic equilibrium was observed using isothermal desorption.