Measurements of cross sections for inelastic collisions between4He+ions

Cross sections for He 2+ production and charge transfer have been measured for collisions between two unexcited He + ions at centre-of-mass energies between 14 and 58 keV. In this range the cross section for He 2+ production rose with increasing energy from 5.3*10 -18 cm 2 to 24*10 -18 cm 2 , whilst the cross section for charge transfer increased from 5.2*10 -18 cm 2 to about 19*10 -18 cm 2 . The measurements of charge transfer were compared with theoretical and experimental results for He(1s 2 )+He 2+ to He + (1s)+He + (1s). Excellent agreement was found which implies that, for interactions between 4 He + ions at these energies, charge transfer proceeds almost exclusively into the ground state.