Electron loss and capture by fast helium ions in noble gases

We have measured charge-changing cross sections with He⁺ and He²⁺ ions impinging upon target gases He, Ne, Ar, and Kr. The energy range of the helium ions was 0.75--4 MeV and the cross sections were obtained either by the initial-growth method or by the attenuation method. The measured values were compared with the corresponding cross sections obtained with equal velocity H⁺ and H projectiles. Deviations from the simple scaling rules usually applied to the capture process are discussed.