Raman and far-infrared study of crystalline 1,1-dichloroethylene, CH2CCl2 and CD2CCl2

Far infrared spectra (30-200 cm -1 ) and Raman spectra (20-3200 cm -1 ) of crystalline CH 2 CCl 2 and CD 2 CCl 2 at 20 and 80 K are reported. The lattice spectra contain 29 Raman- and 15 infrared-active modes, which are assigned on the basis of their isotopic frequency shifts. Crystal field splittings and shifts of internal modes are examined in detail. A centrosymmetric unit cell containing at least eight molecules is indicated by these spectra