The Critical 9365 Å Diffuse Interstellar Band and C 60 + Association

The detection of interstellar C 60 + has been debated for 30 yr. The contested attribution of a weaker diffuse interstellar band (DIB) at 9365 Å was re-evaluated here on the basis of a Pearson correlation relative to 9577 Å, which was previously tied to C 60 + by diverse collaborations. An assessment of 11 sightlines revealed a high correlation amongst 9365–9577 Å equivalent widths ( r = 0.93 ± 0.05), after contamination from an adjacent line was mitigated using both numerical integration and Gaussian fits. In tandem with a recent separate study’s high- r evaluation linking 9577–9632 Å across a sizable baseline: three interrelated DIBs matching C 60 + laboratory findings were independently reaffirmed (9365, 9577, 9632 Å). Yet further investigations are required to strengthen the case via two other weak DIBs disputedly linked to C 60 + , particularly owing to potential overlapping lines arising from an expansive chemical space (PAHs).