Raman Spectra of Polyatomic Gases

Raman spectra of gaseous CO₂, N₂O, NH₃, CH₄ and C₂{H}₄$ have been photographed using the line ${λ}2536$ of mercury as the exciting radiation. Vibrational transitions have been observed in all the gases investigated, and rotational transitions in the cases of N${H}₃$ and C${H}₄$. For the frequency shifts due to the vibrational transitions, the following numerical values (in ${cm}^{{-}1}$) have been found: Raman spectra of liquid N${H}₃$ have been photographed and found to give the two frequency shifts: 3298.4 and 3214.5. In the case of gaseous N${H}₃$, pure rotational transitions lead to a moment of inertia having the value ${I}₀=2.79×{}{10}^{{-}40}$. In the case of methane, the positive and negative branches of the 3022.1 band lead to the value ${I}₀=5.17×{}{10}^{{-}40}$. The relations between these data and infra-red absorption data are discussed.