Electron capture by fast He2+ions in gases

Cross sections for single-electron capture by doubly charged helium ions ( sigma 21 ) have been measured in target gases H 2 , He and Ar. The He 2+ energy range was 1-8 MeV, and the cross sections were measured by the initial-growth method. The measured values of sigma 21 are compared with semi-empirical estimates by Nikolaey (1967) and, in the He 2+ -on-He case, with more elaborate calculations by Belkic and Janey (1973), who used the continuum-distorted-wave approximation. Both theories show a good agreement with the present data.