The Raman Spectra and Molecular Constants of the Hexafluorides of Sulfur, Selenium and Tellurium

Abstract

The Raman spectra of the gaseous and liquid hexafluorides of sulfur, selenium and tellurium were determined (Table I). Three lines for each substance were observed and this is the number permitted by the selection rules for a regular octahedral molecule. Frequency formulae based on central forces were derived, and these, together with the appearance of the spectra, were used to assign the observed frequencies to the proper modes of vibration. Estimates of the magnitudes of the forbidden frequencies were made. A provisional value of —238,000 cal. is given for the free energy of formation of SF6 (g) at 25°.