Detection of Carbon-chain Triple Molecules, $C_{n}o(n=2,4,6,8)$, by PDN-FTMW Spectrosopy

Author Institution: Department of Pure and Applied Sciences, College of Arts and Sciences, The University of Tokyo; Faculty of Liberal Arts, Shizuoka UniversityRotational spectra of $C_{n}O (n = 2,4,6$, and 8) have been observed by using a Fabry-Perot type Fourier-transform microwave (FTMW) spectrometer cooperated with a pulsed discharge nozzle (PDN). The molecules have been generated by a pulsed electric discharge of $C_{3}O_{2}$ diluted in Ar, and then adiabatically cooled to $\approx$ 2 K in a subsequent supersonic expansion. All the observed spectra of those species have been analyzed as linear molecules in the ${^{3}}\sigma$-electronic ground state. The determined molecular constants, such as rotational, spin-spin coupling, and centrifugal distortion constants, have provided information on the C=C bond lengths, energy gaps between the excited ${^{1}}\Sigma^{+}$ electronic state and the ${^{3}}\Sigma^{-}$ ground state, and rigidity of the molecules in respect of the bending vibrations