Simple formula for the cross sections of resonant charge transfer between atoms and their positive ions at low impact velocity

The cross sections of resonant charge transfer between atoms and positive ions for all non-transition-elements in the range of low collision velocities (10⁸ cm/sec) have been calculated by the impact-parameter and close-coupling methods. The calculated results are in fairly good agreement with the experimental results for the elements for which data are available. In these results the relation between the cross sections and the ionization potentials of elements was found, and based on this relation a useful and simple formula for the cross section was successfully obtained.