Same as Fig. 7 but for cloud components at υ_LSR = 51 (top), 57 (centre) and 61 km s⁻¹ (bottom), respectively. While the colour map and contours in red displays the 1, 2, and 3σ levels of the χ² distributions of the modelled line ratios between the 3.264 and 3.349 GHz lines (R₁), the 3.335 and 3.349 GHz lines (R₂), and those between the 701 and 724 MHz (R₃), the contours in grey with varying line styles mark the observed line ratios of R₃ for fixed values of N(CH) (as labelled) corresponding to the population in the excited level. The solid light blue curve marks the N(CH) value of the excited state for which the model is best constrained.