Knowledge Bank

The Raman spectra of solid $C2H4$, $C2D4$ and various mixed crystals have been obtained. In addition to the predicted splitting of the intramolecular fundamentals, five of the six expected librational lattice modes were observed for each pure crystal. Two different $C2h5$ crystal space groups have been suggested for solid ethylene. The structural implications of the observed spectra will be discussed in terms of the spectra predicted by model calculations of the relative Raman intensities and the lattice mode frequencies.