[en] Rare gas ions Ne⁺, Ar⁺ and Kr⁺ are injected into a drift tube which is filled with helium gas and cooled by liquid helium. Helium cluster ions RgHe_x⁺ (Rg=Ne, Ar and Kr, x≤14) are observed as products. Information regarding the stability of RgHe_x⁺ is obtained from drift field dependence of the size distribution of the clusters, and magic numbers are determined. The magic numbers are x=11 and 13 for NeHe_x⁺ and x=12 for ArHe_x⁺ and KrHe_x⁺. NeHe_x⁺, Ar⁺ and Kr⁺ are proposed as the core ions for NeHe₁₃⁺, ArHe₁₂⁺ and KrHe₁₂⁺, respectively. (orig.)