Mechanism of chemisorption and interface penetration in reactive systems at low temperatures

In the transport mechanism discussed it is demonstrated that in the large gradients of the chemical potential that exist in reactive systems gas atoms should be able to migrate in a perpendicular direction up to several atomic distances below the surface by non-activated processes. The exponential decrease in the sticking probability s observed after an initial stage with a constant s value of about unity is correlated with the increase of the activation energy barrier between molecules in the gas phase and in the chemisorbed state on the surface. Quantitative experimental results of the kinetic of chemisorption processes recently obtained for oxygen and nitrogen systems support the qualitative and semiquantitative statements of the mechanism proposed.