The visible spectrum of jet-cooled CF3NO

We have observed fluorescence excitation and dispersed emission spectra for the A←X transition of CF3NO cooled in a supersonic expansion. The analysis of these spectra provide torsional energy levels both for the excited electronic state in a staggered conformer and the ground state in its eclipsed conformer. There is no evidence for any other conformer. An energy level calculation of the torsional motion shows that a simple cosine potential having a threefold barrier almost fits the data, but that significant discrepancies remain. Approximate barrier parameters, within the constraints of a simple cosine, are ?3 = 202±10 cm−1 and F = 2.23±0.10 cm−1 for the ground state and ?3 = 533±30 cm−1 and F = 2.12±0.16 cm−1 for the excited state. We discuss evidence for the vibrational normal coordiantes being dependent on torsional level and point out some unexplained intensity anomalies observed in emission to levels above the barrier in the ground state.