Spectroscopic investigation of vibration–rotation bands in acetaldehyde:: Focus on the nν3 (n=1–5) aldehyde CH stretch bands Original Research Article

We describe experiments on acetaldehyde (12CH312CH16O) resulting in new or improved spectroscopic data on the nν3 (n=1–5) aldehyde CH stretching vibrational bands. The n=1 component is rotationally resolved using room temperature and supersonic jet Fourier transform spectroscopy, and vibration–rotation assignments are reported. The next two components (n=2, 3) are recorded at room temperature using Fourier transform spectroscopy, and the K-structure is resolved and assigned. The last two series of bands (n=4, 5) are observed but not resolved, using laser opto-acoustic spectroscopy. Effective vibrational constants (ω̃eff3=2938.53 cm−1, xeff33=55.75 cm−1) are obtained. Information is also provided on additional bands in the spectrum from 1300 to 14 000 cm−1, involving, in particular, the assignment of the K-structure in ν11 and 2ν1, from the jet-cooled and the room-temperature Fourier transform spectral data, respectively. A table updating the origin of most vibration–rotation bands in acetaldehyde previously assigned in the literature is provided.