The high-resolution far-infrared torsional spectrum of ethane

The far-infrared spectrum of gaseous CH3CH3 has been measured at a resoluti on of 0.0016 cm(-1) using a Fourier transform spectrometer. The spectrum wa s recorded with an absorption pathlength of 172 m. The temperature and pres sure of the sample were 294 K and 10 Torr, respectively. A total of 1072 li nes in the torsional fundamental and the first torsional hot band were iden tified. The spectrum shows fully resolved torsion-rotation splittings. As a result, all the torsion-rotation parameters in the zeroth- and the first-o rder Hamiltonian were determined. We are therefore in a position to determi ne the torsion-rotation energy for the lowest three torsional states of eth ane very accurately and to reliably predict the energy positions for the hi gher torsional states. (C) 2001 Academic Press.