Theoretical aspects of thermal desorption

Theory has concentrated on trying to predict the more difficult parameter in the basic kinetic equation, i.e. the pre-exponential factor. Two major approaches have been used. 

The simple form of the Polanyi—Wigner equation is based on the assumption that any particle possessing the requisite activation energy desorbs during the period of a single vibration. If the recombination mechanism is written as 

If the total number of sites available for adsorption is Na, then [A] [B] = Naf(d) where f(0) is some function involving coverage. Thus 

Such relationships indicate two types of behaviour. First, considering the non-dissociative adsorption  

For the dissociatively adsorbed case, several possibilities exist  

---