ESTIMATION OF CROSS-SECTIONS FOR ENERGY-TRANSFER IN BIMOLECULAR COLLISIONS

The proper definition of a cross section for energy transfer in bimolecular collisions is considered. Three models transforming smooth impact parameter dependence into hit or miss cross section form are discussed. The property dependence of the concept of a collision cross section is investigated. Translational energy cross sections (viscosity, diffusion, deflection energy) are found to be smaller than internal energy cross sections (thermal conductivity, thermal activation). An effective potential analysis of the concept of cross section shows that both radial and rotational collisions must be considered. Properly defined theoretical (effective potential, MD simulation) and experimental cross sections for Br2-Br2 show satisfactory agreement.