In the accommodation of plasma reactions, we have included two new rate-expression forms in Gas-phase Kinetics. These fits require auxiliary keywords to specify additional parameters and to distinguish the rate expression from the default of a modified Arrhenius form.

One form includes a polynomial fit to the logarithm of the temperature on which the reaction depends, as follows:

(3–49)

This form is consistent with the rate-constant fits for electron-hydrogen and electron-helium processes in a publication by Janev, Langer, Evans, and Post, [25] when the Arrhenius parameters and are zero. The user can specify this rate-constant fit option using the auxiliary keyword JAN, followed by the nine parameters.

A second form introduces a power series within the exponential of a modified Arrhenius expression, as follows:

(3–50)

The user may specify this rate-constant expression using the auxiliary keyword FIT1, followed by the four parameters. The use of auxiliary keywords are described in more detail in the Auxiliary Reaction Data of the Chemkin Input Manual .