Infrared laser spectroscopy of CCO: the ν3 band of the a1Δ electronic state and 3ν3–2ν3 band of the ground electronic state

The rotationally resolved infrared spectrum of the ν3 fundamental band of the long-lived a1Δ electronic state of the CCO radical has been measured between 1030 and 1105 cm−1 using a tunable diode laser spectrometer. Metastable CCO was produced in a discharge through a flowing mixture of carbon suboxide and helium. Forty-six rovibrational transitions in the P- and R-branches and the four lowest J-lines in the Q-branch were measured. The band origin was determined to be 1082.03134(19) cm−1. In addition, 40 rovibrational lines belonging to the 3ν3–2ν3 band of the ground electronic state were measured. The band origin for 3ν3–2ν3 was determined to be 1056.97894(94) cm−1. The measurements in this band together with previously reported frequencies in the C–C and C–O stretching regions were analyzed to determine harmonic frequencies and anharmonicity constants.