T. Motylewski et al., Gas-phase electronic spectra of carbon-chain radicals compared with diffuse interstellar band observations, ASTROPHYS J, 531(1), 2000, pp. 312-320
This paper compares laboratory gas-phase spectra of neutral and cationic li
near carbon-chain radicals with astronomical diffuse interstellar band (DIB
) spectra. The origin bands of the strong electronic transitions of the stu
died species, C2nH (n = 3-6), HC2nH+ (n = 2-4), NC2n-2N+ (n = 3, 4), do not
coincide with detectable DIBs, except for HC2n-1N+ (n = 3), which possibly
matches a weak feature. It is concluded that the column densities of these
species through the observed diffuse clouds are below 2 x 10(12) cm(-2). T
he profile change and the shift of the maxima of the absorption bands with
temperature are illustrated. The relation to radio-astronomical detection o
f carbon chains in diffuse media is also discussed.