Measurements of positive ion conversion and removal reactions relating to the Jovian ionosphere

Measured rates are presented for the reaction of He⁺ ions with H₂ (and D₂) molecules to form H⁺, H₂⁺, and HeH⁺ ions, as well as for the subsequent reactions of H⁺ and HeH⁺ ions with H₂ to form H₃⁺. The neutralization of H₃⁺ (and H₅⁺) ions by dissociative recombination with electrons is shown to be fast. The reaction He⁺ + H₂ is slow (k = 1.1 × 10^?13 cm³/sec at300°K) and produces principally H⁺ by the dissociative charge transfer branch. It is concluded that there may be a serious bottleneck in the conversion of two of the primary ions of the upper Jovian ionosphere, H⁺ and He⁺ (which recombine slowly), to the rapidly recombining H₃⁺ ion (αH₃⁺]?3.4 × 10^?7 cm³/sec at 150°K).