Visible absorptions of potential diffuse ISM hydrocarbons: C$_9$H$_9$   and C$_9$H$_5$ radicals
  The laboratory detection of previously unobserved resonance-stabilized C$_9$H$_5$ and C$_9$H$_9$ radicals in the supersonic expansion of a hydrocarbon discharge source is reported. The radicals are tentatively assigned as acetylenic-substituted cyclopentadienyl C$_9$H$_5$ and vinyl-substituted benzyl C$_9$H$_9$ species. They are found to feature visible absorption bands that coincide with a few very weak diffuse interstellar bands toward HD183143 and HD204827. 
Mathias Steglich, Surajit Maity, John P. Maier
physics.chem-ph astro-ph.IM