Theory of thermal unimolecular reactions at low pressures. II. Strong collision rate constants. Applications

Abstract

Theoretical expressions for the strong collision rate constants of thermal unimolecular reactions at low pressures k₀^sc are discussed. The rate constant is split up into various factors: a basic expression for a simplified harmonic oscillator model, a factor accounting for anharmonicity effects, a factor accounting for the energy dependence of the density of states, an overall rotation factor accounting for the effects of centrifugal barriers, and an internal rotation factor accounting for the barriers of hindered rotors. Simplified and easily applicable expressions for these factors are derived. The theory is applied in detail to many practical examples. The comparison with experimental results demonstrates the large importance of the weak collision effects which have been treated in part I of this article. Empirical values for the weak collision efficiencies β_c are derived and compared with predicted values.