Time resolved numerical solution of the reaction rates for the ionisation fractions of hydrogen, oxygen, and nitrogen (Eqs. (3)–(10)). The initial conditions at t₀ = 0 were $n_{\mathrm{e}}^{\mathrm{init}}=2000{\mathrm{cm}}^{-3}$, $x_{\mathrm{e}}^{\mathrm{init}}=0.1$, $x_{\mathrm{O}}^{\mathrm{init}}=0.1$, and $x_{\mathrm{N}}^{\mathrm{init}}=0.1$. They have already evolved to the values at the starting point of this plot. The reaction equilibrium is reached after τ_eq ≈ 2 × 10¹⁰ s as indicated as pink shaded area. We fix T_e = const = 10 500 K during the simulation.