CALCULATION OF THE TOTAL SCATTERING CROSS-SECTION FOR THE COLLISION OF HARD-SPHERES - THE ATOM DIATOM CASE

A simple expression for the total scattering cross section Q for the collision of A + BC, where A, B, and C are hard spheres, is derived. It is assumed that B and C are initially touching. The result represents an average over all spatial orientations of the diatomic BC. The cross section depends only on the radii of the three spheres. If RB = Rc, the total cross section is given, to a good approximation, by Q = Π(RA + RB ) (R A + 2RB). A number of combining rules for total cross sections involving hard spheres are also derived. In addition, the results for hard spheres are used to develop a very simple procedure for computing classical atom-diatom total cross sections on realistic potential energy surfaces. The method is applied to collisions of H + H2, Li+ + N2, and Li+ + CO, and is seen to work very well. © 1990 American Institute of Physics.