Collisions between Cs⁺ions-a further experimental study

An intersecting-beam technique has been applied to careful remeasurements of the cross section sigma (Cs 2+ ) for Cs 2+ production from the combined processes of charge transfer and ionisation in Cs + -Cs + collisions in the CM energy range 42-271 keV. The authors' results, which involve smaller uncertainties, exhibit some differences but are in general accord with their previously reported values (Dunn et al., 1979) and thereby confirm the discrepancy with the cross sections reported by Peart et al. (1981) in the CM range 19-79 keV. In an attempt to explain this discrepancy the authors also studied collisions of Cs + in Xe (where Xe is isoelectronic with Cs + ) in a beam-static-gas target configuration. Measured cross sections for Cs 2+ formation by one-electron-loss collisions in Xe in the CM energy range are found to have magnitudes comparable with the corresponding values of sigma (Cs 2+ ) in the authors' intersecting-beam experiment. The authors' beam-static-gas target studies have also been used to demonstrate the strong influence of large-angle scattering on the measured cross sections for Cs 2+ formation. An analysis relating the product-ion scattering distribution in experiments of this type to that in an intersecting-beam experiment is presented and used to illustrate the need to take proper account of product-ion scattering. The results of this analysis indicate that the much smaller cross sections sigma (Cs 2+ ) recorded by Peart et al. are a consequence of inadequate allowance for the contribution from large-scale scattering.