Excitation diagrams of H₂ derived along the MRS background lines of sight, excluding the flagged data. The column densities of each rotational level are derived from the corresponding line intensities using Eq. (A.1) and are normalized and color-coded by the H₂ column density estimated in Appendix B. For visual clarity, data points are slightly offset along the energy axis by small random values. Detections, along a given line of sight, of all successive rotational transitions up to at least the S(3) line are connected by segments.