g/d = 1000 model spectrum is decomposed into its main molecular constituents. We use the notation “OH_H” for ro-vibrational OH lines from the HITRAN database in contrast to the pure rotational lines computed in non-LTE and denoted by “OH”. These single molecule spectra are convolved to R = 600 and arbitrarily shifted, but not scaled except for C₂H₂ and HCN. The C₂H₂ lines around 13.7 μm are very weak in the model, and are amplified by a factor of ten in this figure to make them visible. The vertical coloured lines and top labels identify the molecules and ions in the same way as in Fig. 4.