title: Rotational spectra of the carbon-chain radicals HC5O, HC6O, and HC7O.
abstract: Three new free carbon-chain radicals, HC5O, HC6O, and HC7O, and their deuterated isotopic species have been observed by Fourier transform microwave spectroscopy of a supersonic molecular beam. In contrast to the shorter HCnO radicals, these all have linear heavy-atom backbones and 2Pi electronic ground states. Like the isovalent HCnS radicals, the ground states of the HCnO radicals alternate with odd and even numbers of carbon atoms: those of HC5O and HC7O are 2Pi1/2 and that of HC6O is 2Pi3/2. From frequency measurements between 6 and 26 GHz, the rotational constant B, the centrifugal distortion constant D, and the lambda-type doubling and magnetic hyperfine constants have been determined to high precision for each chain. Predicted properties from coupled-cluster calculations are also reported for chains up to HC9O. The production of HCnO radicals for n even was highly favored when O2 was used as the source of oxygen, but those with n odd were best produced with CO.
authors.affiliation: Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Mail Stop 72, Cambridge, Massachusetts 02138, USA.
authors.forename: S
authors.initials: S
authors.lastname: Mohamed
authors.forename: M C
authors.initials: MC
authors.lastname: McCarthy
authors.forename: A L
authors.initials: AL
authors.lastname: Cooksy
authors.forename: C
authors.initials: C
authors.lastname: Hinton
authors.forename: P
authors.initials: P
authors.lastname: Thaddeus