High resolution of the nu /sub 7/+ nu /sub 8/ band of ethylene (C/sub 2/H/sub 4/) at 1889 cm/sup -1/

Abstract

The nu /sub 7/+ nu /sub 8/ A-type band of C/sub 2/H/sub 4/ has been recorded between 1932 and 1847 cm /sup -1/ with a resolution of 0.06 cm/sup -1/. The transitions with /b K//sub -1/<or=8 and /b J/<or=25 have have been assigned. Although slight Coriolis resonances perturb the band, the analysis has been made easy through the use of an elaborate set of asymmetric top computer programmes. The band centre and a set of upper state constants have been obtained. 288 observed upper state energy levels have been fitted with a standard deviation of 0.021 cm/sup -1 /. All the resonance effects perturbing the levels of ethylene near 2000 cm/sup -1/ have been predicted. This led to the identification of the nu /sub 4/+ nu /sub 8/ and nu /sub 8/+ nu /sub 10/ combination bands in low resolution spectra.Anglai