The far-infrared spectrum of acrolein, CH2CHCHO: The ν18 fundamental and (ν17 + ν18) − ν18 hot bands

The ν18 fundamental band (∼158 cm−1) of acrolein is studied at high resolution (0.0015 cm−1) using synchrotron radiation from the Canadian Light Source facility and a Bruker IFS 125HR Fourier transform spectrometer. By fitting this band, together with some pure rotational transitions, molecular parameters are obtained to accurately determine the energies of the ν18 = 1 state levels for values of (J, Ka) up to at least (45, 24). These parameters should be useful for future high resolution studies of acrolein hot bands. This is demonstrated here by a detailed analysis of the (ν17 + ν18) − ν18 hot band at ∼589 cm−1. The upper state (ν17 + ν18) of this band is found to be perturbed by Coriolis interactions analogous to those affecting the ν17 state.