MOLPOP-CEP non-LTE radiative-transfer modelling of the CH ground-state transitions towards the broad (left) and narrow (right) velocity components observed towards the CP in TMC-1 for N(CH) = 5 × 10¹³ cm⁻² (top panel) and 5 × 10¹⁴ cm⁻² (bottom panel). Displayed in red and blue solid and dashed curves are the modelled line ratios which best reproduce the observed line ratios between the 3.264 GHz and 3.349 GHz lines and the 3.335 GHz and 3.349 GHz lines and their uncertainties, respectively, as a function of n and T_kin. The dashed teal line marks the upper limit for the gas temperatures for the broad and narrow features.