SIMBAD references

Only recently have groups of diffuse interstellar bands (DIBs) been observed to have regular structure lending new hope for the identification of the bands' origins. Herbig has reported a group of bands between 6770 and 6860 A which seem to show regular spacing and intensity alternation. We suggest that these bands resemble perpendicular vibronic bands in a molecule of the form CH2X. As the Herbig group lies very near an expected transition of similar form in thioformaldehyde, CH2S, an analysis of the absorption spectrum of that molecule was made to determine if it had other bands in common with the DIB spectrum. Six prominent, red-shaded, sharp, single-headed bands were calculated, based on laboratory data, to have absolute frequency positions within 2 cm^-1 of those for the corresponding DIBs. The transitions would originate from the 2y_3 level in the ground electronic state of thioformaldehyde, suggesting that vibrationally hot bands in the transition A1A2 ← X1A1, may correspond to a number of DIBs. Although no absorption features are seen from a vibrationally cold ground state, only a few thioformaldehyde bands expected to be more intense than those suggested to be in the DIB spectra have not been observed to date. There are no significant inconsistencies between corresonding thioformaldehyde bands and DIBs with respect to establishing DIB families. The corresponding bands also generally agree in their shapes and expected intensities. The DIBs appear slighly narrower than the thioformaldehyde bands even if the latter were from a rotationally cold molecule.