Calculated spectroscopic constants for the X 3Σ−, 1Δ, 1Σ+, 3Π, and 1Π states of CCO. The heat of formation of CCO

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Abstract
Geometries, excitation energies, and vibrational frequencies have been calculated for the X 3Σ−, 1Δ, 1Σ+, 3Π and 1Π states of CCO using POL–CI wave functions based on GVB wave functions with a polarized valence double zeta basis set. The results are compared to known spectroscopic constants for the X 3Σ− and 3Π states of CCO. The calculated Te’s (experimental values in parenthesis) are 0.95 eV for 1Δ, 1.58 eV for 1Σ+, 1.49 eV (1.44) for 3Π and 3.49 eV for 1Π. The calculated vibrational frequencies are ν1=1838 cm−1 (1978), ν2=367 cm−1 (379.4), ν3=1086 cm−1 (1074) for X 3Σ− and ν1=1841 cm−1 (2045.7), ν2=580 cm−1 (607.8), ν3=1097 cm−1 (∼1270) for 3Π. The Do (C–CO) is calculated to be 30.6 kcal/mole with an estimated error of ∼23 kcal/mole (based on comparable calculations for ketene) leading to an estimated Do (C–CO) of 54 kcal/mole and a ΔH°fo of 89 kcal/mole.