The synthesis of benzene in the protoplanetary nebulae CRL618

Wood P.M., Millar T.J., Zijlstra A.A., Herbst E., 2002, ApJ, 574, L167

Abstract

We show that the physical conditions in CRL 618 are such that efficient formation of benzene, C₆H₆, occurs. A combination of high temperatures, high densities, and high ionization rates drives an efficient ion-molecule chemistry involving condensation reactions of acetylene and its derivatives, rather than reactions involving atomic hydrogen, as was suggested for the interstellar synthesis of benzene. We find a column density of benzene within a factor of 2 of that observed providing that the material is trapped in a long-lived reservoir of gas in the disk around CRL 618. We note that the chemistry can give rise to other carbon chain molecules as well as a large abundance of benzonitrile, C₆H₅CN.

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