Detection and Structure of Carbon-Chain Singlet Molecules, $C_{n}O(n=5,7,9)$, by PDN-FTMW spectroscopy

Author Institution: Faculty of Liberal Arts, Shi Zuoka University; Department of Pure and Applied Sciences, College of Arts and Sciences, The University of TokyoRotational spectra of $C_{3}O_{2} C_{7}O_{5}$ and $C_{9}O$ have been observed by using a Fabry-Perot type Fourier transform microwave (FTMW) spectrometer cooperated with a pulse-discharge-nozzle (PDN). The molecules, produced by the discharge of $C_{3}O_{2}$ diluted in Ar, exhibit a spectrum characteristic of a linear-molecule in a singlet electronic state, For the $C_{5}O$ molecule, spectra of the normal and all the single isotope substituted species have been assigned, leading to a substitution structure. The $r_{5}$--structure and the structure calculated by an {ab initio} MO theory for the $C_{5}O$ molecule are compared and discussed. The average C--C bond lengths in the $C_{7}O$ and $C_{9}O$ molecules have been calculated by assuming the same partial structure as that in the $C_{5}O$ molecule