Ratio log₁₀(I_obs/I_mod) for the FeI (red diamonds) and NiI (blue squares) lines measured in comet 3I for observations secured with UVES on August 28 (top) and September 12 (bottom). I_obs represents the observed line intensities and I_mod the intensities computed with the fluorescence model. I_obs/I_mod is proportional to the column density of the atoms (Manfroid et al. 2021). The separation between the mean values computed for NiI and FeI gives the NiI/FeI abundance ratio. The ratios have been shifted on the y-axis so that the mean value of log₁₀(I_obs/I_mod) is zero for FeI.