Resolved torsional splitting in the ν18 and ν19- bands of propene

FT-jet spectra of propene were recorded at 0.005 cm−1 instrumental resolution around 950 cm-1. Thanks to the jet conditions, probably corresponding to Trot close to 80 K, the torsion degrees of freedom are efficiently cooled down and the fine structure of the ν18 and ν19 vibrational bands could be investigated. The bands are perturbed and approximate variation of the principal rotational constants are obtained, as well as band origins. The A/E torsional splitting appears totally unpredictable over the range of vibrational-torsional energy investigated.