Sample of model spectra of Fe I, Fe II, Ti I and Ti II in green, brown, red and blue respectively, over a 13 nm slice of the HARPS-N spectral range. These spectra are calculated assuming an isothermal atmosphere at 4000 K between pressures of 10 to 10⁻¹⁵ bars and abundances correponding to the solar metallicity value (Sect. 3.3). A full overview of all the calculated model spectra is provided in Fig. C.1. Together, these figures serve to show the rich absorption spectra caused by the presence of these atoms in the atmosphere of KELT-9 b.