2001A&A...377.1063G

We used spectra of several bright, reddened stars, most of them likely to be obscured by individual interstellar clouds, to examine the proposition that C₇^– may carry several diffuse interstellar bands (DIBs) (Tulej et al., 1998ApJ...506L..69T). To search for the broad features of the C₇^–B ← X system we used low resolution, very high S/N spectra, but even in heavily reddened objects the predicted bands remain undetectable. High resolution (R=80000) spectra prove that the diffuse bands, found in close vicinity of narrow lines belonging to the A ← X system, show variable strength ratios from object to object which proves that they are not of the same origin. The paper brings thus evidence that the C₇^– molecule does not cause any of the detected DIBs.