Potential energy diagram, adsorption process

The potential energy diagram was therefore modified following suggestions by Ertl, on the basis that, under the conditions of temperature and pressure required for industrial ammonia synthesis, the dissociative adsorption of nitrogen becomes an activated process. The potential energy diagram is reported in Fig. 4.13. While there is no direct experimental evidence for this postulate, it is noteworthy that the same basic assumption was taken by Temkin for the development of his kinetic equation. ... 

The adsorption can be represented energetically through the Lennard-Jones diagram [17], displaying the potential energy of the system during the adsorption process, starting from the initial position of both the metal and of the molecule, as shown in Fig. 4.15. 

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