Vibrational spectroscopy and force field calculations in Si2F6

The infrared (IR) and Raman spectra of gaseous Si 2 F 6 have been measured in the spectral range from 150 to 4400 cm −1 and from 30 to 2000 cm −1 , respectively. We have found that the doubly degenerate antisymmetric vibrations are not only IR but also Raman active. The previously assigned D 3 d structure of the molecule is therefore questionable and other possible structures are discussed. The torsional frequency has been indirectly measured to be 38 cm −1 . Values for the harmonic force field constants have been obtained with the Wilson's F-G matrix method and compared with a previous calculation. Coriolis coupling constants, vibrational amplitudes and isotopic shifts have also been estimated.