On angular momentum decoupling approximations and factorization in diatom–diatom scattering

Angular momentum decoupling approximations for rotor–rotor collisions are investigated. The coupled states and infinite order sudden approximations are derived from a novel point of view. In addition to ordinary cross section, the CS and IOS results for relaxation cross sections in molecular gaseous mixtures are obtained. It is shown that the full IOS leads to factorization of the scattering amplitude, integral and differential cross sections, and the nonresonant relaxation cross sections. Limited test calculations of the factorization for degeneracy averaged integral cross sections are reported for the o-H2+p-H2 system.