To account for ion-impact energy on a reaction-rate, the following general form is available, as well as the more specific ion-yield form described in Ion-enhanced Reaction Yield Expression . For the general functional form, the reaction-rate constant can be modified as follows:

(4–30)

In this case, the reaction rate depends upon a threshold energy, , and the energy expressions can be raised to a specified power in two different ways through the use of the parameters and . Ion-energy dependent reactions are declared in the Pre-processor input via the auxiliary keyword ENRGDEP. An executable can find out which reactions were declared as ion-energy-dependent reactions and get an array of the parameters by a call to SKIENR. Because the subroutines that evaluate rate constants in Surface Kinetics take temperature as an argument, and not species energy, subroutine SKRPAR must be called to input an array of ion energies, ENRGI before the rate constant routine is called. Use of the ENRGDEP keyword is only allowed for irreversible reactions.