Resonance ionization spectroscopy of HCO and DCO. II. The B̃ 2A′ state

Abstract

Resonance two-photon ionization (R2PI) spectroscopy of the HCO B̃←X̃ ‘‘hydrocarbon flame’’ band system performed with a jet-cooled molecular beam at 5 K has permitted the assignment of subband origins for 17 vibronic bands of HCO and 20 of DCO. Term values, the three harmonic vibrational frequencies and six anharmonicity constants are measured for the B̃ 2A′ states of both molecules. The observation of an increase in the effective asymmetric top rotational constant, A–(B+C)/2, with increasing vibrational quantum number identifies the B̃ state bending vibration with fundamental frequencies of 1382 and 1213 cm−1 for HCO and DCO, respectively. The highest fundamental frequencies of 2597 cm−1 for HCO and 1944 cm−1 for DCO correspond to CH(CD) stretching, while the lowest fundamental frequencies of 1066 cm−1 for HCO and 922 cm−1 for DCO correspond to the vibration of singly bonded C–O.