Main excitation and de-excitation routes computed with MADEX, assuming N(CH⁺) = 10¹³    cm^-2, υ_exp = 1 km s^-1, n_H = 10⁴ cm^-3, and (a) T_K = 100 K, χ_fir = 1, χ_nir = 1, and χ_opt = 1, (b) T_K = 1000 K, χ_fir = 1, χ_nir = 1, and χ_opt = 1, (c) T_K = 100 K, χ_fir = 10⁶, χ_nir = 1, and χ_opt = 1, (d) T_K = 100 K, χ_fir = 1, χ_nir = 10¹⁰, and χ_opt = 1, (e) T_K = 100 K, χ_fir = 1, χ_nir = 1, and χ_opt = 10⁶. The photodissociation process was intentionally neglected to focus on the (de)excitation of the bound-bound rovibronic transitions. The pure rotational, rovibrational, and rovibronic transitions are displayed in blue, purple, and red. Nonreactive and reactive collisional processes are displayed in green and yellow. In each case, the levels that do not contribute to the excitation of the pure rotational levels are not displayed (e.g. Λ, υ, J = 0, 1, 0 in the case (d)). For more clarity the rotational emission lines from J = 10 to J = 5 are merged into a single dotted arrow in case (b), and all vibronic Λ,J = 1,1 ← 0,0 absorption lines and Λ,J = 1,1 → 0,2 emission lines are merged into two single arrows in case (e).