Spectrum (black crosses) and synthetic profiles of the CH and C₂ bands computed with A(C) = 6.8 and 7.4 for the CH band, and A(C) = 7.1 and A(C) = 7.4 for the C₂ band (blue lines). The red line represents the synthetic spectrum computed with the adopted value of the C abundance in this region of the spectrum (A(C) = 7.28 for the C₂ band and 7.25 for this region of the CH band; see Table A.1). The abscissa is the wavelength in nm. Shown on the red side of the C₂ band is the good fit of the Mg triplet obtained with A(Mg) = 6.6.