Comparison of cross-sections from the Leiden Observatory database for photochemistry (Heays et al. 2017) for the photo-ionisation of СI and the photo-dissociation of CO (gold curves top and bottom, respectively, with right-hand ordinates) with SEDs of the attenuated stellar photosphere (green) and the interstellar radiation field (purple) at 10¹⁶ cm from the star (with left-hand ordinate). The corresponding dotted curves refer to the unattenuated and undiluted radiations fields. Dust extinction coefficients were calculated from Rouleau & Martin (1991). The frequency scale is linear, so as to enhance its high-frequency end.