Knowledge Bank

Rotational spectra of $C3O2C7O5$ and $C9O$ 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 $C3O2$ diluted in Ar, exhibit a spectrum characteristic of a linear-molecule in a singlet electronic state, For the $C5O$ molecule, spectra of the normal and all the single isotope substituted species have been assigned, leading to a substitution structure. The $r5$--structure and the structure calculated by an {ab initio} MO theory for the $C5O$ molecule are compared and discussed. The average C--C bond lengths in the $C7O$ and $C9O$ molecules have been calculated by assuming the same partial structure as that in the $C5O$ molecule.