Raman spectra of asymmetric top molecules

A detailed analysis of the Raman-active v 1, v 3 (both A-type) and v 5 (Bc -type) vibration-rotation bands of ethylene is presented. In addition to structural data simulation of the spectra yields values for the polarizability ratios of the totally symmetric bands, giving information on the polarizability ellipsoid as the molecule vibrates. v 3 is shown to be perturbed by a c-type Coriolis interaction which complicates the interpretation of the negative value of the polarizability ratio required to match the observed spectrum. The effects of asymmetry are pronounced; one result being the formation of heads in the R,PR K p and R,P P K p branches of low K p in the v 5 band.