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Abstract:
We describe thermal desorption experiments and their computer simulations together with thermodynamic equilibrium measurements for molecular nitrogen adsorption on an Fe{111} surface. Three distinct nitrogen adsorption states, labeled δ, γ, and α with increasing desorption temperature, are detected and it is found that adsorption into the π‐bonded α state occurs via the δ and γ states at low substrate temperatures. The δ state can act as a precursor for the γ state at T <100 K, but at higher temperatures the direct channel from the gas phase into the γ state predominates the adsorption/desorption kinetics. The activation energy of desorption for γ‐N2 is found to be ∼10% lower than the isosteric heat of adsorption indicating the possibility of dynamical effects in the desorption process into vacuum. It was also observed that preadsorbed α‐N2 increases the heat of adsorption for γ‐N2 which is evidence for a mutually attractive interaction between those two states.
