NON-ARRHENIUS RATE CONSTANTS IN HIGHLY EXOTHERMIC REACTIONS

Highly exothermic chemical reactions can produce chemical species with much kinetic energy. Since the Arrhenius expression for the rate constant is based on the assumption that the kinetic energy distribution is approximately a Maxwellian, a study has been carried out to determine if the Arrhenius expression is always valid for chemical reactions initiated by products of highly exothermic reactions. A Monte Carlo method was used to estimate the rate constants of chemical reactions initiated by energetic species and it was found that the rate constant could be much greater that its Arrhenius value. Under certain conditions it is shown that the non-Arrhenius rate constant as a function of temperature is given approximately by a simple dimensionless group.