HIGH RESOLUTION RAMAN SPECTROSCOPY OF GASES: XII. ROTATIONAL SPECTRA OF C2H4 AND C2D4 AND THE STRUCTURE OF THE ETHYLENE MOLECULE
The pure rotational Raman spectra of C2H4 and C2D4 were photographed in the second order of a 21-ft grating. The resolution achieved was such that several lines due to single transitions were observed (and identified) in the spectra of both molecules. An analysis of these lines based on the non-rigid asymmetric top yielded the following rotational constants for the ground states:[Formula: see text]The structural parameters obtained from these constants are r0(C=C) = 1.339 ± 0.002 Å, r0(C—H) = 1.086 ± 0.003 Å, and [Formula: see text]. These values are in agreement with the recent preliminary results of the electron diffraction data. There is also agreement between the above values and those obtained from a recent study of the rotation–vibration spectra of C2H4 and C2D4, although the agreement between the ground state rotational constants is not as satisfactory.