Kinetic Order of Desorption Process

If desorption takes place from a surface displaying the heterogeneity required by the Elovich equation, then for a first-order desorption process, the rate is given by 

01 = 1 and 02 = 0.5 and a jRT equal to 5, the error is reduced from 23 to about 8%, and for the short 0 range, 1 to 0.9, to a maximum of 1%. In general, account should be taken of the variation of the pre-exponential term in evaluating a for small values ( 3 kcal/mole). 

The possibility of determining the kinetic order of a desorption process having a variation of activation energy with coverage is extremely small since even with a very small value of 8, the exponential term may dominate the kinetics. As an example, we presume a second-order molecular desorption from a homogeneous surface covered with adatoms where there is a small induced heterogeneity that varies with coverage. 

Even on a uniform surface, it is difficult to distinguish a second order from a first-order process when 0 1, and when only a small range of 0 

---