Peculiarities of atom–quasidiatom collision complex formation: classical trajectory study

Abstract

General peculiarities in the formation of quasibound complexes (QC) in collisions of an atom with a rigid diatomic or linear polyatomic molecule are studied using the method of classical trajectories. The CO2–Ar system is taken as an example. Statistical distributions of parameters characterizing either the formation of QC or those appropriate to rotational relaxation cross-sections are simulated and analyzed. Various factors are examined as far as their role in the formation of the QC is concerned: (1) the complexity of a trajectory approach (exact classical, planar, coplanar); (2) the selection of intermolecular potential energy surface (ab initio Parker–Snow–Pack potential; empirical Berreby–Dayan potential); (3) the departure of the initial CO2 rotational distribution from equilibrium. The cross-sections and bimolecular thermal rates for QC formation are obtained using the modified Sorbie–Murrell model. The use of derived analytical expressions makes the computations of QC fractions in CO2–Ar collisions easier both in equilibrium and in rotational non-equilibrium conditions.