Electronic Spectroscopy of Carbon Chains

The characteristic electronic transitions involving π−π excitation have been identified for a number of homologous series of carbon chains. These include neutral species, H- and N-substituted derivatives, and ions. The absorption spectra were observed in an inert neon environment at 5 K using the approach that combines mass selection with matrix isolation spectroscopy. The understanding of the spectral pattern in the electronic transitions of carbon chains suggests the types and sizes that should be considered in connection with astronomical observations. The location of the band systems in neon matrixes has also opened the way to gas-phase studies. The first measurements on the electronic transitions of neutral carbon chain radicals by cavity ringdown spectroscopy as well as on carbon chain anions by a resonant two-photon detachment method have been made. The relevance of the spectra to the diffuse interstellar bands is illustrated.