Rotational structure in the Ã1A″–1A′ spectrum of formyl chloride
High-resolution cavity ring-down spectroscopy has been used to record three vibronic bands of the Ã1A″–1A′ (π*â†�nO) transition of room-temperature formyl chloride (HClCO). These three bands (601, 501601 and 201501601) are all vibronically induced through the activity of the out-of-plane inversion vibration ν6, and are found to obey type-a selection rules. Rotational constants have been derived from the analysis of these bands and used to give information on the geometrical structure of the excited state. The properties of the Ãstate are found to be intermediate between those of the corresponding states of formaldehyde and formyl fluoride.