The infrared spectra of acetonitrile and acetonitrile-d3 have been studied at − 50°C for the high-temperature (β) crystalline phase and at − 65°, − 115° and − 192°C for the low-temperature (α) crystalline phase. A powder x-ray pattern obtained at liquid-nitrogen temperature indicates that the unit cell is primitive orthorhombic and that it contains eight molecules. It is shown that the consideration of all available structural data together with the site group and factor group splittings for the α crystal tends to favor D2h1 (Pmmm) and D2h9 (Pbam) as possible space groups.

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A synthesis of spectral evidence and x-ray data has resulted in the solution of the crystal structure of the a form of hexafluoroethane. The space group is C2h2 with two molecules in the unit cell located on Ci sites. The unit-cell dimensions are a = 9.3 Å, b = 5.1 Å, and c = 4.6 Å. There is disorder in the a crystal which was determined to be of the statistical variety. The spectra of the a form verified the symmetry aspects of the theory governing solid-state vibrational spectroscopy, but the approximate dipole-dipole theory was shown to partially fail in explaining even the relative magnitudes of the splittings in the nondegenerate modes. This failure was ascribed to atom-atom interactions in the crystal.

The Raman spectrum of hexafluoroethane in the liquid phase has been obtained. The polarization of the lines appearing in the spectrum has been measured qualitatively. An assignment of the frequencies has been made from the spectrum.