Monte Carlo simulation of RRKM unimolecular decomposition in molecular beam experiments. III. Application to angular distributions and branching fractions for the system K + CsF

Abstract

The experiments on the reactive systems K + CsF and K + RbF by Stolte et al. are unique in that product angular distributions and branching fractions with variation of both translational and rotational energies have been obtained. The results for the reaction K + CsF with translational energy variation have now been re-evaluated using an algorithm recently published by us. A satisfactory fit to the experimental data is found by a long-lived collision complex model including strict angular momentum conservation in both the reactive and the non-reactive channels. No “osculating” behaviour has to be added to the model. Angular momentum limits have to be included in the model to reach agreement with the measured branching fractions and cross sections. This indicates that the internal dynamics of the complexes is important. The calculation shows that the reactants giving reactive complexes have large rotational and vibrational energies, while their translational energy is nearly average. The internal energy of reactive pairs of molecules decreases with increasing translational energy. The question how rapidly the branching fraction varies with translational energy is thus more complicated to answer than believed previously.