2010MNRAS.408.1590K

In this paper, we present new data with interstellar C₂(Phillips bands A ¹ Π_u-X¹ Σ⁺_g), from observations made with the Ultraviolet-Visual Echelle Spectrograph of the European Southern Observatory. We have determined the interstellar column densities and excitation temperatures of C₂ for nine Galactic lines. For seven of these, C₂has never been observed before, so in this case the still small sample of interstellar clouds (26 lines of sight), where a detailed analysis of C₂ excitation has been made, has increased significantly. This paper is a continuation of previous works where interstellar molecules (C₂ and diffuse interstellar bands) have been analysed. Because the sample of interstellar clouds with C₂ has increased, we can show that the width and shape of the profiles of some diffuse interstellar bands (6196 and 5797 Å) apparently depend on the gas kinetic and rotational temperatures of C₂; the profiles are broader because of the higher values of the gas kinetic and rotational temperatures of C₂. There are also diffuse interstellar bands (4964 and 5850 Å) for which this effect does not exist.