Correlation diagram for candidate C₂ DIBs (blue dots, Table B.3) and possible C₂-related DIBs (green diamonds, Table B.4) compared to reference C₂ DIBs (black squares, Table B.1), candidate C₂ DIBs from the literature (grey diamonds, Table B.2), possible DIBs similar to λ5849 (F5849, cyan triangles), and to a comparison sample of ζ DIBs (Fan et al. 2022, red dots). The horizontal axis displays the normalised anticorrelation Pearson coefficient, kn₆₀₀₉, with the σ DIB λ6009 (excluding the sight lines of HD 175156 and HD 148579). The vertical axis displays the average correlation coefficient, knq_C2 (Eq. (3)), with a subsample of six reference C₂ DIBs (λλ4726, 4963, 4984, 5418, 5512, and 5546). The selection criteria (Eqs. (4,5); dotted blue lines) distinguish C₂ DIBs well from ζ DIBs. Most C₂ DIBs and related DIBs are significantly anticorrelated with σ DIBs (kn₆₀₀₉ < 0). See Fig. B.1 for an extended version of this figure, including the DIB labels.