Charge transfer and formation of metastable He+(2S) ions in collisions of3He2+ions with potassium

The formation of He + (2S) metastable ions by one-electron capture in passage of 10-60 keV 3 He 2+ ions through potassium vapour has been investigated. Absolute cross-sections for He + (2S) formation, believed to be accurate to within a factor of two, have been obtained together with total cross-sections for one and two-electron capture. The results have been compared with similar measurements in argon which is representative of a number of gas targets previously investigated. The growth of He + (2S) ions from 3 He 2+ beams as the target thickness of potassium is increased has also been investigated. The maximum fractional yield of He + (2S) ions observed at 30 keV is 1.2%, which compares with the yield of 2.5% previously obtained from an H 2 target.