Quantum-mechanical calculations on termolecular association reactions XY+Z+M→XYZ+M:: Application to ozone formation

We present a quantum-mechanical model for termolecular association reactions XY+Z+M-->XYZ+M involving the formation of a long-lived complex XYZ*. The rotation of the molecule XYZ is treated in the infinite order sudden approximation (IOS) and its vibrations are treated by the coupled-channel method (VCC). Resonances featuring the XYZ* long-lived complex formation are first computed by means of the stabilization method and are then included in the vibrational basis functions used for the inelastic VCC-IOS scattering calculation. The method yields rate constants for the association process selected in resonance and bound states of XYZ. We apply the method to the formation of ozone and investigate isotope effects. Calculations of energy transfer and collision-induced recombination of O+O(2) in collision with Ar are reported for a range of ozone isotopomers. The bending mode of O(3) is not treated explicitly in these computations. The results establish a strong selectivity in vibrational state-to-state cross sections for the deactivation of O(3) during the collisional energy transfer process with Ar. The present calculations also account for the high sensitivity of rate constants with respect to the isotopic composition of ozone molecules but not in the same proportion as experiments. The energy transfer from selected initial vibrational states is also calculated as a function of the initial relative kinetic energy. (C) 2002 American Institute of Physics.