The [Formula: see text] electronic absorption spectra of acetaldehyde-h4 and -d4 were recorded in the vapour phase at room temperature. The major experimental requirement was a high pressure × path length (650 Torr × 140 m). The vibrational structure of these electronic transitions was interpreted in terms of the torsional modes [Formula: see text] and [Formula: see text] attached to the [Formula: see text] out-of-plane bending mode. The main CH3CHO results agreed with those obtained earlier (Moule and Ng); the values of the [Formula: see text] transition and torsional barrier height were 27240.1 and 590 cm−1 respectively. Three inversion (out-of-plane bending) energy levels in the excited [Formula: see text] state were found and the inversion potential function was determined with a barrier height of 1110 cm−1. The CD3CDO spectrum confirmed the CH3CHO analysis. The values of the [Formula: see text] transition and torsional barrier height were equal to 27270 and 610 cm−1. Keywords: vibronic spectrum, acetaldehyde, molecular structure.
ACCURATE TORSIONAL BARRIER HEIGHT OF TRIFLUROACETIC ACID
