Infra-Red Spectrum of Tetradeuteroethylene

Abstract

THE molecule C₂D₄ has twelve fundamental modes of vibration, of which six should be observable in Raman scattering, five in infra-red absorption, while the remaining one must be deduced from combination frequencies in the infra-red or from measurements of specific heat. A knowledge of those is of considerable interest in the theory of molecular vibrations (a) as a qualitative check on the assignment of the fundamental frequencies of the C₂H₄ molecule, (b) as a test of various potential functions which have been advanced to correlate the frequencies of C₂H₄. Of those twelve frequencies, so far only four have been reported, being recently observed in the Raman spectrum by de Hemptinne, Jungers and Delfosse¹. We now wish to report briefly an investigation in the infra-red by which we have identified another four of the twelve fundamentals.