General distorted-wave treatment of rotational transitions in molecular collisions

Abstract

An iterative procedure is described for the determination of the cross-sections for rotational transitions in the collision of two diatomic molecules. The first iteration yields the familiar distorted-wave (d.w.) approximation, which has already been applied to the two principal transitions in parahydrogen. The iteration has now been carried a stage further, yielding what may be termed the second d.w. approximation; with the use of the same intermolecular potential function as gave reasonable agreement with experiment in the previous calculation, it is found that the cross-sections at thermal energies are decreased by about 8%. It is therefore concluded that the first d.w. approximation is adequate for the treatment of rotational relaxation in hydrogen at and below room temperatures.