Visible absorptions of potential diffuse ISM hydrocarbons: C$_9$H$_9$ and C$_9$H$_5$ radicals

TL;DR

This study reports the laboratory detection of new C9H5 and C9H9 radicals with visible absorption features that match some diffuse interstellar bands, advancing understanding of interstellar hydrocarbons.

Contribution

It presents the first laboratory identification of specific C9H5 and C9H9 radicals and links their absorption spectra to diffuse interstellar bands.

Findings

Detected C9H5 and C9H9 radicals in the lab.

Their absorption spectra match some diffuse interstellar bands.

Provides insight into interstellar hydrocarbon chemistry.

Abstract

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.