Active-site models and their sensitivity to radiation

2 Active-site models and their sensitivity to radiation 

Models which regard solid surfaces as non-uniform, in the sense of containing different sub-sets of surface sites distinguishable from each other by virtue of their local structure and topography, and which associate widely different activities with these subsets, have long been termed active-site models [31—33]. The applicability of this type of model to individual catalysed reactions has been the subject of controversy [12b], 

Bernasek and Somorjai proposed that, as the temperature increased and the surface concentration of the D2(ads) species decreased, an Eley— Rideal-type mechanism became important, involving direct reaction of an incident gas phase D2 molecule with H atoms present at the stepped active sites, having (Id ) as the r.d.p. and obeying the rate expression 

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