Collision Integrals for Soft, Nonspherical Molecules in Terms of Spherical Ω* Integrals

A new formulation of the classical kinetic theory of dilute gases composed of molecules with rotational structure is given which closely parallels that for structureless molecules. The matrix elements of the collision operator are expressed as integral moments of a generalized collision cross section 𝒥. It is shown that a suitable approximation for the momentum dependence of 𝒥 leads to expressions for the matrix elements which can be written in terms of the familiar spherical Ω* integrals.