Raman Spectra of Compounds in the Gaseous and Liquid States

Abstract

An apparatus for exciting the Raman spectra of gases and liquids at temperatures up to 300°C is described. For phosphorus trichloride, methyl chloride, methyl bromide, methyl alcohol, methylene chloride, methylene bromide, chloroform, and carbon tetrachloride, the Raman spectra of the gas and the liquid at the same temperature have been photographed in juxtaposition with a liquid-prism spectrograph of speed f: 2.9 and linear dispersion 27A/mm at 4400A. The Raman spectra of gaseous n-pentane, n-hexane, and deuterium oxide have been photographed with 2537A excitation. The change in the Raman frequencies with the state of aggregation is different for different vibrations and varies greatly from compound to compound. In the absence of an adequate theory for this phenomenon, a search has been made for empirical regularities. The perpendicular bands of the symmetrical-top molecules are much less diffuse in the liquid than in the gas, showing that the intermolecular forces are effective in quenching the rotation of the molecules in the liquid. The other bands are about equally sharp in gas and liquid.