The Raman and infrared spectra of CF4 have been recorded in its liquid and two crystalline phases. In the liquid, rotational wings along side some of the fundamentals and the appearance of some forbidden infrared bands reveal the high degree of molecular disorder characteristic of this phase. Very little change occurs in the spectra at the liquid–solid transition; the spectra of Phase I thus appear to be those of a plastic crystal. Marked changes are observed upon cooling to Phase II. The splitting of the fundamentals in the Phase II spectra of CF4 is best interpreted in terms of a S4 tetragonal structure, with the molecules lying on sites of S4 symmetry.

Can. J. Chem. 72,587 (1 994).Monoligand complexes of nickel atoms with simple alkynes have been investigated by kinetic studies of association reactions of nickel atoms with ethyne, propyne, and 2-butyne in the gas phase near room temperature, and by quantum chemical calculations on the Ni[C2H2] complex using a Linear Combination of Gaussian-Type Orbitals -Density Functional (LCGTO-DF) method. Experimental estimates of binding energies of the monoligand complexes have been made by using RRKM unimolecular reaction theory to model the pressure dependence of second-order rate coefficients for the association [Traduit par la rCdaction]

The i.r. and Raman spectra of liquid and crystalline SiH4 and SiD4–SiH4 mixtures have been recorded. The spectra show striking changes when the crystal undergoes the solid–solid phase transition. Phase I is disordered. Possible site, and factor groups for the low temperature crystalline phase are proposed.

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The Raman and infrared spectra of liquid and crystalline SiF, have been recorded. The assignment of some of the Raman bands of the crystal to longitudinal modes has been confirmed by the infrared reflection spectrum. These indicate that the crystal structure is not centrosymmetric. In other respects the spectra are also more complicated than is expected on the basis of the previously reported Td3 structure. Possible explanations are discussed.On a enregistre les spectres Raman et infrarouges de SiF4 dans ses Ctats condenses. Certaines bandes Raman du cristal, attribuCes a des modes longitudinaux de par le spectre de reflexion infrarouge, indiquent que la structure du cristal n'est pas centrosymetrique. Les spectres sont par ailleurs plus compliquCs que ceux predits d'apres la structure cristalline Td3 proposCe antkrieurement. On apporte quelques explications a ces anomalies.