Approximate Quantum Mechanical Calculation of Reactive Scattering Cross Sections - The Fixed Angle Reactor Model (FARM)

Abstract

An approximate three-dimensional quantum mechanical method for the calculation of atom-diatom reactive scattering cross sections and rate constants is described. The method is known as the Fixed Angle Reactor Model (FARM). Its key features are that it uses information from both classical trajectory and simplified quantum mechanical calculations to compute vibrational state-to-state reactive scattering cross sections. The classical trajectory calculations are used to estimate the degree to which torques acting during the approach of the collision partners are able to successfully reorient them into the most favorable geometry for subsequent reaction. This information is then used, together with fixed angle quantum reactive scattering calculations to approximate a full three-dimensional quantum reactive scattering calculation. Test results are presented for the reactions: H + H2(ν = 0) → H2(ν' = 0) + H and D + H2(ν = 1) → HD + H and comparison is made with other methods.