title: A new interstellar molecule:  tricarbon monoxide.
abstract: The cold dark interstellar Taurus Molecular Cloud One (TMC-1) is a rich source of acetylenic and polyacetylenic molecular species.  As well as linear closed-shell molecules (H(C triple bond C)nCN) and symmetric rotors (CH3C triple bond CH, CH3C triple bond CCN), several radicals (C triple bond CH, C triple bond CCN, (C triple bond C2H) have also been identified, many of which had not been studied previously in the laboratory.  Whether the observed abundances can be understood in terms of purely gas-phase ion-molecule chemical schemes, which produce  reasonable agreement for the simplest polyatomic species, is unclear; alternative models involving the particulate interstellar grains as catalysts or sources have also been suggested.  We now report the detection in TMC-1 of a new molecule, tricarbon monoxide (C3O), whose pure rotational spectrum has only very recently been studied in the laboratory.  As C3O is the first known interstellar carbon chain molecule to contain oxygen, its existence places an important new constraint on chemical schemes for cold interstellar clouds.  In fact, the observed abundance of tricarbon monoxide fits quite well into our model of galactochemistry.
authors.affiliation: Herzberg Institute for Astrophysics, National Research Council of Canada, Ottawa.
authors.forename: H E
authors.initials: HE
authors.lastname: Matthews
authors.forename: W M
authors.initials: WM
authors.lastname: Irvine
authors.forename: P
authors.initials: P
authors.lastname: Friberg
authors.forename: R D
authors.initials: RD
authors.lastname: Brown
authors.forename: P D
authors.initials: PD
authors.lastname: Godfrey
mesh_terms: D055580:Astronomical Phenomena; D001256:Astronomy; D002244:Carbon / Q000032:analysis / Q000737:chemistry*; D002248:Carbon Monoxide / Q000032:analysis* / Q000737:chemistry*; D019443:Cosmic Dust / Q000032:analysis*; D005118:Extraterrestrial Environment
chemical_list: D019443:Cosmic Dust; D002244:Carbon; D002248:Carbon Monoxide