Raman Spectra of Polyatomic Gases

Abstract

Raman spectra of gaseous C${\mathrm{O}}_{2}$, ${\mathrm{N}}_{2}$O, N${\mathrm{H}}_{3}$, C${\mathrm{H}}_{4}$ and ${\mathrm{C}}_{2}$${\mathrm{H}}_{4}$ have been photographed using the line $\ensuremath{\lambda}2536$ of mercury as the exciting radiation. Vibrational transitions have been observed in all the gases investigated, and rotational transitions in the cases of N${\mathrm{H}}_{3}$ and C${\mathrm{H}}_{4}$. For the frequency shifts due to the vibrational transitions, the following numerical values (in ${\mathrm{cm}}^{\ensuremath{-}1}$) have been found: Raman spectra of liquid N${\mathrm{H}}_{3}$ have been photographed and found to give the two frequency shifts: 3298.4 and 3214.5. In the case of gaseous N${\mathrm{H}}_{3}$, pure rotational transitions lead to a moment of inertia having the value ${I}_{0}=2.79\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}$. In the case of methane, the positive and negative branches of the 3022.1 band lead to the value ${I}_{0}=5.17\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}$. The relations between these data and infra-red absorption data are discussed.