SiCCO and CCCO: accurate equilibrium structures and spectroscopic constants

Cubic force fields have been calculated for SiCCO and CCCO by means of the coupled cluster variant CCSD(T) and Dunning's cc-pVQZ basis set. There from, a variety of spectroscopic constants (harmonic vibrational wavenumbers, vibration-rotation coupling constants, l-type doubling constants and equilibrium quartic centrifugal distortion constants) has been computed. Accurate equilibrium structures are established for both molecules and precise predictions are made for the ground-state rotational constants of less abundant isotopomers of SiCCO.