Comparison of the theoretical blue line wings of the resonance line of K (dotted lines) with the experimental spectra (full lines). The red curve represents K–He and the black curve represents K–H₂. The density of perturbers is 10¹⁹ cm⁻³ at 800 K. The experimental spectra show the K₂ dimer absorption. Detail of the spectrum of ϵ Indi Ba shows the blue satellite of the K resonance lines (observational data of Mark McCaughrean, as was described in Allard et al. 2007a).