Profile of the 12.2 μm line observed in Arcturus by Sundqvist et al. (black circles) and compared with our calculations using the ⟨ 3D ⟩ _1D atmospheric model and the non-LTE abundance taken from Table 9. The black lines show synthetic profiles using different model atoms (see Table 8), and are all convolved with a macroturbulent velocity of 5.2 km s^-1 and a rotational broadening of vsini = 2.1 km s^-1. The grey line is the profile using the F model atom but without macroturbulence.