SIMBAD references

The A¹Π_u⟵X¹Σ⁺_gtransition of the simplest polyatomic carbon chain molecule, C₃, at 4051.6 Å has been searched for toward reddened stars where abundant C₂had been reported and toward other stars with high color excess. Absorption from C₃has been detected toward 15 stars with color excess E(B-V) from 0.33 to 1.12. The observed C₃column densities, ranging from 10¹² to 10¹³ cm^–2, are well correlated with the corresponding C₂column densities, with N(C₂)/N(C₃)∼40, indicating their close chemical relation. The carbon-rich sight line toward HD 204827 (for which no previous C₂observation had been reported) has by far the highest C₃and C₂column densities. The chemistry of formation of C₃ from C₂is discussed. A search for the next strongest 020-000 vibronic band was unsuccessful as a result of the low Franck-Condon factor and interference with a stellar line. Searches for C₄and C₅were negative.