Torsional Splittings in the Band ν9+ ν4− ν4of Ethane☆

Abstract Torsional splittings of the C 2 H 6 hot band ν 9 + ν 4 − ν 4 have been determined based on measurements taken with the Kitt Peak National Observatory Fourier transform spectrometer with .0025 cm −1 resolution. The measured splittings range from −.2347 cm −1 (the sign is relative to that of the observed splitting in the ν 9 band of C 2 H 6 ) to .0682 cm −1 , with a standard deviation of the observed splittings of .0251 cm −1 . The splittings can be explained as a result of xy Coriolis interaction of ν 9 + ν 4 with the excited torsional states τν 4 , with the major effect arising from the “forbidden” interaction with the nearly degenerate state 5ν 4 ς = 2. The rms error of the predicted splittings is .00422 cm −1 , if parameters determined from theory and previous work are used, and is .00217 cm −1 , if small refinements to the parameters are made based on the measured splittings themselves.