Abstract
In this letter we address the issue of the relation between critical distances of negative and positive ion formation during a collisional charge exchange between a large polyatomic projectile and a metallic surface. Based on the ‘freezing distance’ approximation, we have derived a simple expression relating the distances of negative and positive ion formation with the corresponding ionization potential and electron affinity of the neutral molecule. We test this expression by a comparison with experimental values measured for C60–surface scattering, the only system for which distances of formation of both molecular ionic states have been measured. A good agreement with experiment is found.
Acknowledgements
This research was supported by grants from the Israeli Science Foundation (ISF) and the German–Israeli Binational James Franck Program.