The modified connection formulae for the rotational transition cross sections in diatomic molecules for slow collisions

The formulae connecting the cross sections (or the rate constants) for various rotational transitions in diatomic molecules colliding with atomic particles were discussed in the authors' earlier paper (1981) and are valid in the framework of the sudden approximation. In order to extend the applicability domain of these formulae to the slow-collision region a semi-empirical correction factor is introduced with an exponential dependence on the translation-rotation energy transfer and on the inverse collision velocity (or the inverse square root of the temperature). The modified connection formulae are applied to the rotational transitions in an HD molecule colliding with an H 2 molecule. The parameters entering the connection formulae are fitted to the effective potential calculations of Chu (1975). Another application based on the experimental data of Sudbo and Loy (1982) is made for NO-NO collisions where both the rotational and electronic spin-orbit states of the molecule are changed.