SIMBAD references

Several unidentified infrared emission bands (UIBs) have been assigned to neutral C₆₀ molecules present in circumstellar and interstellar environments. However, due to the similarity of the infrared (IR) spectra of C₆₀ in the solid state and in the gas phase, as of yet there is no consensus on the aggregation state of C₆₀. In this article, we show that even strong covalent chemical bonding might have very little influence on the IR spectrum of C₆₀, and that therefore such chemically bonded C₆₀ could be the carrier of the same UIBs. It would best explain observations like the missing emission from C₆₀ ions and a large variation of relative band intensities between different sources. We demonstrate that such a chemically bonded C₆₀ can be produced by the co-condensation of C atoms together with C₆₀ molecules, which leads to the formation of a three-dimensional C₆₀ polymer film. Such polymerized C₆₀ molecules cannot easily desorb, while their spectral properties in the visible and IR spectral ranges are almost undisturbed by polymerization.