Direct Simulation Monte Carlo Modeling of High Energy Chemistry in Molecular Beams: Chemistry Models and Flowfield Effects

摘要

Benchmark state-to-state vibrational energy excitation cross sections have been calculated for O + CO. The rate constants derived from these cross sections agree with available equilibrium measurements, but the cross sections extend to much higher energies. These benchmark cross sections provide an opportunity to test a widely used DSMC chemistry model at a detailed level and provide insight on one of its adjustable parameters. It is shown that extrapolations to the higher energy regime can be in error by an order of magnitude or more. The benchmark cross sections are used in direct simulation Monte Carlo (DSMC) modeling of molecular beam experiments. The simulations are intended to remove a major source of experimental uncertainty in the rates derived from molecular beam measurements by computing local concentrations of reactants in the molecular beam chamber. Furthermore, by keeping track of multi-collision events in the reaction chamber, the present simulations will allow experiments to be designed which increase the amount of reactants beyond the single-collision regime normally employed, greatly extending the range of molecular beam measurements that can be made.