Gas‐Phase Electronic Spectra of Carbon‐Chain Radicals Compared with Diffuse Interstellar Band Observations

Abstract

This paper compares laboratory gas-phase spectra of neutral and cationiclinear carbon-chain radicals with astronomical diffuse interstellar band(DIB) spectra. The origin bands of the strong electronic transitions ofthe studied species, C_{2n}H (n=3-6),HC_{2n}H^{+} (n=2-4), NC_{2n-2}N^{+}(n=3, 4), do not coincide with detectable DIBs, except forHC_{2n-1}N^{+} (n=3), which possibly matches a weakfeature. It is concluded that the column densities of these speciesthrough the observed diffuse clouds are below 2x10^{12}cm^{-2}. The profile change and the shift of the maxima of theabsorption bands with temperature are illustrated. The relation toradio-astronomical detection of carbon chains in diffuse media is alsodiscussed.