INTENSITY ANALYSIS OF THE TORSIONAL SPECTRUM OF CH3CH3

The far-infrared spectrum of gaseous CH3CH3 has been measured in the region of the torsional fundamental under relatively large pressure-path length conditions. Observations were made at resolutions of 0.08, 0.02, and 0.016 cm-1 and under various experimental conditions using two different Fourier transform spectrometers. In addition, a very high resolution (0.0014 cm-1) spectrum of the lowest lying degenerate fundamental nu-9 was obtained. From a frequency analysis of the far-infrared spectrum and 737 lower state combination differences in nu-9 and its associated hot band nu-9 + nu-4 - nu-4, an improved set of torsion-rotation parameters was obtained. An intensity analysis of the torsional bands was carried out to obtain torsional dipole moments. The torsional dipole components mu-perpendicular-to and (mu-parallel-to - mu-perpendicular-to) were determined to be 9.37(70) and -31.7(2.0) mu-D, respectively. These experimental values are in good agreement with calculated values of mu-perpendicular-to = 10.13 mu-D and (mu-parallel-to - mu-perpendicular-to) = -35.10-mu-D. The shape of the torsional bands can be reproduced in detail with the model adopted here.