Variation of the predicted abundance ratios [HOC⁺]/[H₂O], [HCO⁺ ]/[H₂O], and [CF⁺]/[HF] as a functionof the fraction of molecular gas f(H₂) and the kinetic temperature. The plot is using enhanced capture rates for reactions between ions and polar molecules using the formalism and the molecular data described by Woon & Herbst (2009) and the new theoretical reaction rate for reaction R5 (Denis-Alpizar et al. 2018). Contour levels are set at 2 × 10⁻³, 4 × 10⁻³, 8 × 10⁻³,... up to 128 × 10⁻³. The mean values of the abundance ratios are listed in Table 5.