Specific intensities of the first ten rotational lines of CH⁺ (from J = 1 →0 to J = 10 → 9) as functions of the upper level energy expressed in Kelvin, emitted by two shocks propagating at 5 (red squares) and 10 (blue circles) km s⁻¹ in a medium with density of 10⁴ cm⁻³ and illuminated by a radiation field G₀ = 10² at a visual extinction (top panel) and 0.1 (bottom panel). All other parameters are set to their standard values (see Table 1). The predictions are shown with (dashed) and without (solid) taking into account the UV pumping of the rovibrational levels of H₂. The corresponding frequency of each rotational line is indicated above the figure.