ELECTRONIC SPECTROSCOPY OF CARBON CHAINS

The characteristic electronic transitions involving pi-pi excitation h ave 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 environme nt at 5 K using the approach that combines mass selection with matrix isolation spectroscopy. The understanding of the spectral pattern in t he electronic transitions of carbon chains suggests the types and size s that should be considered in connection with astronomical observatio ns. 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 spect roscopy as well as on carbon chain anions by a resonant two-photon det achment method have been made. The relevance of the spectra to the dif fuse interstellar bands is illustrated.