Hard-Sphere Model for the Dissociation of Diatomic Molecules

A simple classical model for the activation of diatomic molecules interacting with a heat bath of monatomic particles is proposed. The diatomic molecules are considered as hard spheres connected by springs and the monatomic particles as hard spheres. The model permits strongly nonadiabatic interaction, and because of its simplicity it makes possible a detailed calculation, which takes into account the energy transfer to translational, rotational, and vibrational degrees of freedom. The only parameters in the theory are the gas-kinetic hard-sphere radii of the atoms and the experimentally known activation energy. Comparison with experiments on the dissociation of molecules as I2, Br2, O2, and H2 in the inert gases shows an excellent numerical agreement, as well as a satisfactory dependence of the rate constant on the mass and temperature.