Top: CH₃OCH₃/HCOOCH₃ ratio as a function of time for different ionisation rate values (in units of s⁻¹). Bottom: CH₃OCH₃ and HCOOCH₃ abundances with respect to CH₃OH as a functionof time for different ionisation rate values ζ. The ionisation rates in the upper and lower panel are the same: the solid lines correspond to ζ=3×10⁻¹⁷ s⁻¹, the dashed lines correspond to ζ=3×10⁻¹⁶ s⁻¹, and the dot-dashed lines correspond to ζ=3×10⁻¹⁴ s⁻¹.