Full excitation diagram of Fe II within December 6, 1997 comet showing measured column-density of various energy levels inferred from the measured absorptions and the parameters obtained in Sect. 5.1 (blue dots), the theoretical energy distribution at LTE (red line), and the theoretical energy distribution with an electron density of 3 × 10⁷ cm⁻³ for a few representative energy levels as computed using ChiantiPy (purple dots).