Electronic Spectroscopy of Monocyclic Carbon Ring Cations for Astrochemical Consideration.

Gas phase electronic spectra of pure carbon cations generated by laser vaporization of graphite in a supersonic jet and cooled to below 10 K and tagged with helium atoms in a cryogenic trap are presented. The measured C-He with from 6 to 14, are believed to be monocyclic ring structures and possess an origin band wavelength that shifts linearly with the number of carbon atoms, as recently demonstrated through N tagging by Buntine et al. ( 2021, 155, 214302). The set of data presented here further constrains the spectral characteristics inferred for the bare C ions to facilitate astronomical searches for them in diffuse clouds by absorption spectroscopy.