The High-Resolution Far-Infrared Torsional Spectrum of Ethane

Abstract The far-infrared spectrum of gaseous CH3CH3 has been measured at a resolution of 0.0016 cm−1 using a Fourier transform spectrometer. The spectrum was recorded with an absorption pathlength of 172 m. The temperature and pressure of the sample were 294 K and 10 Torr, respectively. A total of 1072 lines in the torsional fundamental and the first torsional hot band were identified. The spectrum shows fully resolved torsion–rotation splittings. As a result, all the torsion–rotation parameters in the zeroth- and the first-order Hamiltonian were determined. We are therefore in a position to determine the torsion–rotation energy for the lowest three torsional states of ethane very accurately and to reliably predict the energy positions for the higher torsional states.

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